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 West York Borough police officer and a gunman were killed in a shooting Saturday morning that injured multiple staffers at UPMC Memorial Hospital in York County, Pennsylvania, the district attorney said.

Authorities described the shooting of a gunman who opened fire at a Pennsylvania hospital as “absolutely justified, beyond any and all doubt.”

A gunman who held medical staff hostage before killing a police officer and wounding five others at a hospital in south-central Pennsylvania Saturday is believed to have visited the facility in the days leading up to the incident,

Pennsylvania Governor Josh Shapiro met with the family of fallen West York Borough officer Andrew Duarte and the victims of Saturday's shooting at UPMC Memorial Hospital in York County. The governor shared on Saturday evening that he "had the privilege of spending time with Officer Duarte's parents and fellow officers to express our deep gratitude for Andrew and his service.

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.

A man who took workers hostage at a Pennsylvania hospital's intensive care unit was shot dead by police in a shootout that also left one officer dead. Three workers were injured in the attack at UPMC Memorial Hospital on Saturday,