(Story updated at 8:25 p.m. ET.)
A doctor who was grazed by gunfire from a patient in his office at a suburban Philadelphia hospital on Thursday helped stop him by apparently returning fire with his own weapon and severely injuring him, but not before a caseworker was killed, authorities said.
The patient opened fire after entering the office with the caseworker, District Attorney Jack Whelan said. Witnesses reported hearing yelling before the gunshots.
Several hours after the shooting, investigators had only limited information on what happened inside the closed office but believe the doctor, a psychiatrist, "from all accounts, would have acted in self-defense," Whelan said.
The doctor, who suffered a graze wound to his head, "faced a situation where his life was in jeopardy," Whelan said.
Yeadon Police Chief Donald Molineux said that, "without a doubt, I believe the doctor saved lives."
"Without that firearm, this guy (the patient) could have went out in the hallway and just walked down the offices until he ran out of ammunition," Molineux said.
The dead caseworker was identified only as a 53-year-old woman who had entered the doctor's office with the patient before the gunfire erupted. Police said they were trying to find relatives to notify.
Two guns were recovered, Whelan said. Authorities said the motive for the shooting was unknown.