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,

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.

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.