Lester Mendoza, who specializes in pulmonary critical care, was present when the perpetrator was informed about his loved one's death.

Lester Mendoza took to Facebook to share his story of interacting with the shooter, Diogenes Archangel-Ortiz, days before he held staff hostage and shot six people, killing a police officer at the hospital.

A gunman took hostages inside a Pennsylvania hospital, fatally shooting a police officer before he was killed by police, officials said.