Investigators are trying to determine why a man targeted a Pennsylvania hospital, taking workers inside the intensive care unit hostage and holding one staff member at gunpoint as her hands were bound by zip ties.

Authorities say a shooter entered UPMC Memorial Hospital's ICU and took staff members hostage before he was killed by police in a shootout.

A police officer was killed Saturday after responding to a shooting at UPMC Memorial Hospital located just outside of Harrisburg, Pennsylvania, where a gunman took several hostages and injured at least five other people before he was shot dead.