Two people wounded by alleged gunman on Memorial Drive in Cambridge

A man opened fire Monday on Memorial Drive, wounding two people and causing an afternoon of mayhem; he was ultimately stopped by a state trooper and an armed civilian, who shot him.

Middlesex County District Attorney Marian Ryan at a press conference Monday evening said the two victims were hospitalized. One is an MBTA van driver, she said, and the other was a man in his car on Memorial Drive.

Ryan said the alleged gunman was on parole and was known to Boston Police, who'd warned Cambridge officials he might be in the area, just before the shooting.

The shooter, identified as Tyler Brown of Boston, allegedly fired 50 to 60 rounds from an assault-style rifle. He was shot, Ryan said, by a state trooper and another person, and was later hospitalized.

Officers had shut down Memorial Drive, as city and state police responded to reports of gunfire near the River Street Bridge around 1:30 p.m.

At the scene of the investigation, local resident Janet Brockenbough told WBUR she'd heard the gunshots when they went off. She pointed out a nearby car under police control that had bullet holes in the windshield.

"I was shocked that this happened here, in this part of Cambridge," she said.

Less than an hour later, the police department posted a notice on Facebook saying there was "no on-going danger to the public," but warned residents to avoid the area. A major police presence remained for hours.

Some Cambridge schools went into lockdown, but those precautions lifted soon after.

Ryan, the district attorney, said she plans to press for further gun controls. Massachusetts has among the strictest gun laws in the nation.