Fortunately, doctor with a gun critically wounded shooter who attacked hospital, gun-free zone sign didn't stop attack

This attack apparently occurred in a gun-free zone.  Here is a great quote from the Philadelphia Inquirer:

"There's a sign on the door that says you have to check your weapons at the front," she said, "But you can't expect every crazy person to do that."

From Fox News about an attack at Mercy Fitzgerald Hospital in Darby, PA that was stopped by Dr. Lee Silverman:

A doctor who was grazed by gunfire from a patient in his office at a suburban 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. . . . 

Another doctor and a caseworker were among those who helped wrestle the patient to the floor of a hallway and grabbed his weapon after he had already been critically wounded from several gunshots, Whelan said. . . .

It seems extremely likely that this doctor was one on the almost 900,000 concealed handgun permit holders in Pennsylvania.  The Associated Press has information on how important that it was that the doctor was armed:

. . . 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," the chief said. . . .

From Channel 13 WGME there is information on how the attack started:

. . . The caseworker killed at Mercy Fitzgerald Hospital on Thursday afternoon was Philadelphia resident Theresa Hunt. Authorities say she had accompanied Plotts to an appointment with Silverman at a psychiatric crisis center next to the hospital in Darby, just southwest of Philadelphia. . . .

CBS News has some more details:

The patient, who had psychiatric problems, opened fire after entering the doctor's office with a caseworker Thursday afternoon, Whelan said. The female caseworker was killed. The doctor appears to have suffered only a graze wound and was expected to be released from treatment later in the day. 

Authorities have not publicly identified the gunman or his two victims. CBS Philly reports Whalen said the gunman was shot three times. Both the doctor and the suspect were taken to the Hospital of the University of Pennsylvania for treatment, according to the station. . . . 

The name of the attacker appears to be Richard Plotts.