Christians were gathered in churches around the world to celebrate Palm Sunday on April 9, 2017, marking the beginning of Holy Week. During this time of year, many Christians share in a renewal of their faith as they remember the pilgrimage that Jesus took before his death and resurrection.

At Saint George Church in Tanta, Egypt, the church was full. Scriptures were read. Songs were sung. Somewhere between welcome and amen, a bomb exploded, killing at least 25 people and wounding dozens of parishioners and members of the clergy.

Investigators reportedly believe, according to CNN and other media reports, that someone had placed an explosive device under a seat in the prayer hall. Exactly how the bomb was detonated is still unknown.

As emergency personnel were working to secure the scene at Saint George, a second attack occurred just outside of St. Mark Coptic Orthodox Cathedral in Alexandria, Egypt.

The church service had just ended and people were leaving the building when a man arrived wearing a zipped-up jacket with one hand in his pocket. A security officer denied the visitor access to the cathedral and referred him to the metal detector outside the church's entrance.

The man can be seen on video talking with the officer and then walking towards the metal detector. He walked a few steps past it, turned, entered the metal detector frame, and detonated a bomb, killing at least 11 people, including three police officers, and wounding 35 others. The actions of the security officer and the use of the metal detector saved numerous lives that day.

Between the two attacks, 43 people died and approximately 100 were injured. ISIS claimed responsibility for both attacks and warned that there would be more attacks in the future against Christians, police, and the military, according to CNN.

However, these attacks left many questions unanswered. Details such as how the bombers picked their targets, whether they were working together, and what advance preparations they had made all remained a mystery.

Did the bombers choose these congregations based on the size of the facilities? It appears that the attackers selected a day in which they knew more people would be present at the churches, possibly in an attempt to create more terror and politicize them as an assault on Christianity. A similar attack at a Christian church in Alexandria on New Year's Day in 2011 killed 21 and injured 96, according to The Telegraph. Christians have been targeted in several attacks in Egypt, which explains the enhanced security precautions in place on Palm Sunday in 2017.

These bombings prompt several questions. What can be done to prevent an attack from occurring in our respective places of worship? Will it become customary to have a bomb-sniffing dog search the premises? Will metal detectors become a common feature outside religious and cultural properties?

There is no commonly accepted or developed profile of a suicide bomber, the Anti-Defamation League (ADL) wrote in Protecting Your Jewish Institution in 2015. The only characteristic accepted by experts is that the overwhelming majority are prepared to die in the service of their cause.

Security leaders are faced with the challenge of preventing an act that someone else is determined to achieve, even in the face of death.

We have known for years that the Islamic State wants to destroy Western culture, and that they plan to attack various locations, including houses of worship, bus stops, airports, hospitals, schools, shopping venues, concert halls, night clubs, parades, sporting events, and other places with large gatherings of people. Additionally, we are experiencing more attacks by individual terrorists with various affiliations, as seen in recent attacks using vehicles in Paris and London.

The ADL reported in January 2017 that bomb threats have increased. In addition, there is an increase in anti-Semitic assaults on college campuses. As a result, the league has updated some of its resources to assist synagogues with their security plans as they seek to secure places of worship, religious artifacts, and those attending services.

The Muslim community is not exempt from crime, and has reported increases in incidents of violence and vandalism, most of which are suspected to be committed by homegrown extremists in response to terror acts committed across the globe. In the Middle East, extremists often target more moderate Muslims as they seek to impose Sharia Law.

Houses of worship around the world are faced with various challenges as they try to secure their facilities, people, and programs with limited budgets and resources. A congregation of 1,000 will have some of the same challenges as a congregation of 100, but it will have more resources. Smaller congregations may not face the same complexities as larger organizations but they may still encounter violence.

For example, when 21-year-old Dylann Roof entered the Emmanuel African Methodist Episcopal Church in Charleston, South Carolina, on June 17, 2015, only 12 parishioners were present.

Every church throughout the world has the same goal: to provide a safe place to worship. We can implement interior and exterior controls and follow best practices to prevent many types of crimes. However, nothing can protect houses of worship from a bombing except denied access.?Bombings in the United States

The most notorious church bombing in the United States occurred in September 1963 in Birmingham, Alabama, at the Sixteenth Street Baptist Church. A bomb exploded in the building, killing four African-American girls during a service and injuring at least 14 others. Three former Ku Klux Klan members were eventually convicted of murder for the bombing.

Between 1970 and 2007, there were 25 terrorist attacks against religious figures or institutions in the United States; nine of the 25 attacks involved explosives or bombings, according to the National Consortium for the Study of Terrorism and Responses to Terrorism (START). Nine of those attacks targeted Jewish institutions.

The FBI also tracks hate crimes against individuals and religious institutions, with a reported 1,402 victims of anti-religious hate crimes in 2015, according to the Uniform Crime Reports: Hate Crime Statistics 2016.

Those crimes primarily targeted Jews (52 percent), Muslims (22 percent), Catholics (4 percent), and individuals of varying religious groups (4 percent).

This was an increase from figures released in 2015, when the FBI reported that there were 1,140 victims of religious hate crimes in the United States. Hate crimes, as defined by the FBI, include traditional crimes, like murder, arson, or vandalism, that are motivated by bias.

For example, in January 2012 in Rutherford, New Jersey, several Molotov cocktails and incendiary devices were thrown at a synagogue, starting a fire in the second-floor bedroom of the rabbi's residence. This was deemed the fourth bias incident in a month against a Jewish religious institution. Other incidents included a fire that was intentionally set and graffiti at two synagogues.

Bombings Suspects

The profile of a bomber in the United States may be different from what security professionals expect. It could be a jilted spouse or lover who is seeking revenge at the end of their romantic involvement. It could be former business partners or employees looking for retribution when a business relationship goes south. It could also be the work of a terrorist,foreign or homegrown, trying to make a political statement toward a specific person or group. 

As of this writing, most bombings in the United States are carried out by an individual working alone. Further investigations after the fact generally indicate that a spouse or family member had suspicions about the bomber's behaviors, but did not seek help.

While security cannot anticipate the moves of a bomber, there are a few behavioral characteristics that could be considered suspicious.

• Nervousness, including sweating, tunnel vision, and repeated, inappropriate prayers or muttering, as well as repeated entrances and exits from the building.

• Inappropriate, oversized, and loose-fitting clothing.

• Concealed hands, such as in pockets, to hold a triggering device.

• Favoring one side or area of the body, as if wearing something unusual or uncomfortable.

• Projected angles under clothing, such as those that would indicate the individual is carrying a firearm at the waist or ankle.

• Constantly adjusting clothing.

• Carrying packages or backpacks.

When this kind of behavior is observed, the "See Something, Say Something" principle is applicable. However, at religious institutions, if at all possible, congregants should be encouraged to leave the area.

Reports should be made to a law enforcement officer if possible. If law enforcement is not available at the location, individuals have the option to investigate on their own, report suspicions to church staff, or do nothing. In these instances, security professionals should trust their instincts.

PREVENTING A BOMBING

The attacker could use a mail bomb or a placed bomb. Placed bombs, like the one used in the Boston Marathon bombing, injure indiscriminately and can be concealed in boxes, backpacks, briefcases, and purses.

There is no certain way to prepare for a bombing. As witnessed with the Boston Marathon bombing, members of the public are vulnerable at events and in crowds. Someone can enter a facility with intent to do harm and there is little security can do to stop him or her.

But, just as Boston responded quickly with paramedics and doctors, houses of worship need to be prepared with security and safety measures.

Places of worship need video cameras for successful identification of attackers. Congregants must be diligent in their observations of attendees who might intend harm. They also need to be observant of behavior that is unusual, such as a person who attempts to enter a church after the service had ended, as the second Palm Sunday bomber did.

As a precautionary step, religious institutions' office personel should be trained about mail bombs and suspicious packages, such as the pipe bomb that was mailed to a Lakewood Church in Houston, Texas, in January 1990.

The pastor's daughter, director of ministries for the church, opened the package addressed to her father, suffering minor burns and bruises, according to The New York Times.

Access control is key to a secure environment, as the Tanta, Egypt, bombing shows. Someone was able to place a bomb inside the sanctuary, showing that someone had access to the facility prior to the start of the service.

Staff should also be advised to keep offices and desks locked when they are not in use to avoid creating hiding places for explosives. Staff should also ensure that utility janitorial closets, boiler rooms, mail rooms, computer offices, switchboards, and elevator control rooms are locked at all times.

Additionally, trash receptacles (especially dumpsters) should be locked and located far from the building. The area around the receptacles should also be free of debris. As demonstrated by the Oklahoma City bombing in 1995, cars and trucks should be required to maintain a safe setback from the facility.

A security plan should also include an evacuation plan for the facility with a designated meeting point to ensure that everyone is safe, should it be used. Places of worship should also be equipped with medically trained staff, first aid kits, and ambulatory services to quickly respond, should an attack take place.

There are no easy answers to this disturbing dilemma. There is no easy way to predict when or where a bombing may occur. There are even fewer ways to prevent it. As security leaders, we must be diligent in our observations of human behavior.

Paula L. Ratliff is the coauthor of Crime Prevention for Houses of Worship, the first book published on the topic in 2001 and the author of the second edition. She began researching crimes against religious facilities in the early 1990s and has written several articles on crime prevention for places of worship. She is a member of ASIS International and a graduate of the University of Louisville.