WASHINGTON — Not long ago, Army veteran Dennis Magnasco would respond with frustration when he saw his more liberal friends publicly call for gun reform. They weren’t experts on the weapons that they wanted banned, he thought. They didn’t understand the nuances.

That all changed Oct. 1, 2017, when a shooter used semi-automatic rifles modified with bump-fire stocks to kill 58 people at a music festival in Las Vegas. Magnasco listened to audio of the shooting. The sound of the gunfire transported him back to his time as a combat medic. It took him back to Afghanistan.

“It shook me to my core because it sounded like combat,” Magnasco said. “I had this feeling of, ‘This isn’t right.’?”

When 17 students and teachers were killed Feb. 14 at Marjory Stoneman Douglas High School in Parkland, Fla., by a 19-year-old using an AR-15 assault-style rifle, Magnasco spoke out.