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

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

The shooter has been identified as Diogenes Archangel Ortiz. He allegedly entered the hospital with a handgun and zip ties.

Anguish and anger at the very recent loss of a loved one apparently spurred on the man who would target the intensive care unit at a Pennsylvania hospital Saturday morning, a senior law enforcement official briefed on the investigation told ABC News.