A mental-health caseworker is dead and a doctor and his patient wounded after a bizarre gunfight at a gun-free-zoned hospital in Yeadon, Pa., near Philadelphia, Thursday. As police prepare murder charges against the wounded patient, focus is shifting to the gun-toting psychiatrist who stopped the mayhem, likely saving other lives.

Prosecutors say Dr. Lee Silverman opened fire on Richard Plotts, after Mr. Plotts shot his caseworker and barged his way toward Dr. Silverman’s office desk after gaining access to Mercy Fitzgerald Hospital. Silverman crouched down behind his desk and fetched his gun, which he then fired at Mr. Plotts, wounding him several times before he was subdued.

In the gunfight, Silverman was grazed in the temple by a bullet. The caseworker allegedly shot by Plotts, Theresa Hunt, died from her wounds, police said. She was transporting Plotts to the hospital for treatment. One of Silverman’s colleagues told the Monitor Friday that he was “surprised” that the Mercy Fitzgerald psychiatrist was armed.

The question of whether it’s a good idea to arm doctors and teachers and others who work in places historically targeted by mass shooters has been recurrent in the news since even before the 2012 Sandy Hook Elementary School massacre in Newtown, Conn.

Gun-control groups, which have found new political footholds after a series of high-profile school shootings, contend that America’s gun violence problem is tied to the sheer numbers and easy-availability of firearms in the US, as well as what they see as increasingly lax laws that allow almost anyone to carry a gun anywhere in the country

But pro-gun forces, led by the National Rifle Association, which have for the most part managed to squelch new national gun-safety legislation in the past two years, have made the opposite argument: that lawfully armed citizens can deter shooters in public places – or, at least, limit the damage they can do.

That contention, to be sure, is up for debate. Yet the Pennsylvania hospital gunfight is already being recounted at least by some gun owners as a telling anecdote about life in a heavily armed nation where 60 million people suffer from some kind of mental-health problem.

For one thing, police are still trying to figure out why Silverman was armed in the first place since bringing a gun to work is against the rules at the hospital.

"We do believe that there were some issues between the doctor and the patient, but whether or not he actually feared him is unclear," said Delaware County District Attorney Jack Whelan.

The decision likely saved lives, police acknowledged. "If he [the doctor] wasn't armed ... this guy could have went out in the hallway and just walked down the offices until he ran out of ammunition,” Yeadon Police Chief Donald Molineux told media.

For gun rights activists, the situation – an armed doctor stops a rampaging patient in a gun-free zone – embodies both the public safety ironies around gun control and also points to what they argue is the real culprit in most public violence in the US: unchecked mental illness.

Many mental-health professionals, meanwhile, argue that ties between mental illness and violence are overblown and inaccurate. They cite a 2001 study of mass murderers that showed only 1 in 4 had any history of mental illness.

“Even if we had a perfect mental-health-care system, that is not going to solve our gun violence problem,” Dr. Jeffrey Swanson, a medical sociologist at the Duke University School of Medicine, told ProPublica last month.

Gun rights bloggers disagree.

“You’d think [the Philadelphia hospital shooting] would make it clear to the other side that the problem lies with our mental health and legal systems,” writes Sebastian, a Pennsylvania resident who runs the influential Shall Not Be Questioned gun blog.

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According to media reports, Plotts had a history of personal problems, including drug abuse, and his arrest records show run-ins with police over weapons violations and suicide attempts. “You could see he needed help,” one neighbor told the Philadelphia Daily News. If Plotts survives his injuries, prosecutors plan to charge him with first-degree murder.

Whether the hospital takes administrative action against Silverman for carrying a gun to work will be closely watched by those involved in America’s febrile gun debate.