Investigators are trying to determine why an armed man targeted a hospital in the US state of Pennsylvania, killing one officer and injuring several medical staffers. Bearing a pistol, the armed man entered the UPMC Memorial Hospital intensive care unit (ICU) on Saturday and took staff hostage prior to his death,

The man who authorities say entered a Pennsylvania hospital with zip ties and a pistol over the weekend had recent contact with the hospital's intensive care unit, where he took staff members hostage and was killed in a shootout that left a police officer dead and others injured.

A gunman, armed with a handgun and carrying zip ties, went inside UPMC's ICU, and took staffers hostage before he was ultimately killed by police in a shootout, the York County DA said.