The gunman who held intensive care unit staff hostage at UPMC Memorial Hospital in Pennsylvania before killing a police officer and injuring five other people Saturday believed that more could have been done to save his wife,

A man who took hostages at UPMC hospital during a shooting that killed a police officer and wounded five others highlights the rising violence against U.S. healthcare workers.

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.

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.

An officer was killed, and six others were injured after a man armed with a pistol and zip ties entered into a Pennsylvania hospital's intensive care unit Saturday afternoon. Police were called to UPMC Memorial Hospital on Innovation Drive and Roosevelt Avenue in York County, Pittsburgh Action News 4's sister station WGAL reported.

Investigators are still 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.

A man who took hostages in a Pennsylvania hospital during a shooting that killed a police officer and wounded five other people highlights the rising violence against U.S. healthcare workers and the challenge of protecting them.