The unease growing inside Nancy Duarte Matarese on Saturday quickly blossomed into full-on dread as she found herself being escorted to a small family room inside WellSpan York Hospital.

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,

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.