While the rallies were at opposite ends of the complex, the two sides squared off briefly in the crowded east-wing Rotunda during the CeaseFirePA event.
In a moment that was more spontaneous confrontation than a snippet of any national conversation on gun violence, Sally Thompson of Glen Mills, Delaware County, took her concerns directly to the gun-rights forces. She didn't have to go far. Some were standing right behind her, holding pro-Second Amendment signs.
"I want you to have a gun," Thompson told a trio of young men, one wearing a shirt emblazoned with a Smith & Wesson logo. "I just want to limit assault weapons."
Paul Saber of New Columbia asked her, "Why can't I have an elite fighting weapon today?"
She replied, "Because too many people are dying."
Saber said he stopped by the CeaseFire rally after the gun-rights rally to hear what the opposition had to say. But he said he does not see room for compromise.
"You take away my right to have a gun and you make me a victim," he said.
Saber's handgun was, at that moment, in the hands of Capitol Police - along with 129 other firearms the gun-rights supporters checked as they entered the building, where all visitors step through metal detectors. No incidents were reported by Capitol Police, said Department of General Services spokesman Troy Thompson.
Earlier, Saber joined the crowd on the front steps to rally against measures under consideration in the Assembly, such as an assault-weapons ban, a limit on purchases to one handgun a month, and a requirement that owners report lost or stolen guns to police. Those measures are sure to face stormy debate in a state where big-city officials have pushed strict gun curbs but firearms owners are a strong and politically active bloc.
State Rep. Daryl Metcalfe (R., Butler), the state's most vocal pro-gun legislator, drew a roar of approval at the rally when he said he had introduced House Bill 357 - named for the .357 Magnum handgun - to bar the state attorney general and other state officials from enforcing any new federal gun laws.
"We're showing the liberal gun-grabbers that they are wrong," Metcalfe said.
The state's new attorney general, Kathleen Kane, a Democrat who supports gun-control measures, said through a spokesman that she had no comment on the bill.
Carl Tobias, a constitutional law expert at the University of Richmond Law School, said such a bill would violate the U.S. Constitution's Supremacy Clause, which gives federal law precedence over conflicting state laws.
At the CeaseFire rally, Philadelphia Deputy Mayor Richard Negrin told the crowd how, in 1979, he saw his father gunned down on a Union City, N.J., street by a person wielding a military-style gun prohibited under the 1994 federal assault weapons ban.
"It's a weapon of mass destruction," Negrin said. "Now you can buy them on the Internet."
Thompson, the gun-control supporter who argued with gun-rights supporters, said she was hoping they would realize "that I am not trying to take their guns away."
Before turning back to listen to another speaker tell of a loved one killed by gunfire, Thompson said, "I'd just like to limit the speed that bullets fly."
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