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.

Officer Christopher Reese, 30, worked for the Virginia Beach Police Department for about three years when he and a second officer, Cameron Girvin, 25, were killed Friday night during a confrontation after a traffic stop, authorities said.