Discovery Communications plans to heighten physical security at its Silver Spring, Maryland, headquarters after last year’s hostage standoff that ended in the death of the perpetrator, The Washington Examinerreports:

Discovery wants to install an 8-foot-tall, gated fence in its public garden and divide its lobby, with separate entrances for employees and visitors, according to company officials and documents submitted to the Montgomery County Planning Board .

James Lee, 43, was a familiar face to employees of the cable network company, based just outside Washington, D.C. They regularly saw him alone outside the building, protest sign in hand, demonstrating to get Discovery Channel to increase programming about environmental issues such as global warming and overpopulation.

Around 1 p.m. on Sept. 1, Lee entered the building’s lobby with packages carried on a dolly. He donned a backpack containing propane canisters, pipe bombs, and gun shells, and brandished a firearm and a second object that police thought might be a “dead man switch,” a device that can activate an bomb when pressure is released—such as if the individual holding it is shot by police, according to areport by The Washington Post. He took a security guard and two other company employees hostage in the lobby.

For nearly four hours Lee negotiated his demands via telephone with Montgomery County Police, seeking airtime on Discovery Channel to air his grievances.  Meanwhile, thorough company emergency and evacuation plans were activated. Employees were first instructed via a public address system to remain at their desks. Later, administrative personnel swept through the building, instructing employees to exit the building via a back stairwell. The building's upper floors emptied successfully.

Shortly before 5 p.m. two hostages made a break. Lee gave chase and two police tactical teams emerged and shot Lee, killing him.