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.

UPMC announced this morning via a Facebook post that it has closed Memorial Hospital in West Manchester Township to visitors in the wake of a hostage incident Saturday that left one police officer dead, two injured and several staff members injured. The health care system did not say when visitors to patients would once again be welcome.

Pennsylvania officials said a man entered the intensive care unit of UPMC Memorial Hospital in York and took staff members hostage before he was killed by police on Saturday. An officer also died in the shooting,