Authorities said that two men in separate vehicles suffered life-threatening gunshot injuries.
The alleged gunman was identified as Tyler Brown of Boston. He was shot in the extremities after a State Police trooper and an armed civilian confronted him and opened fire, Ryan said shortly after 7 p.m. during a press briefing at the city’s Police Department. Brown was being treated in the intensive care unit of a local hospital, she said.
Witnesses recalled the terrifying sound of gunfire in the middle of the afternoon near the campuses of Harvard University and the Massachusetts Institute of Technology. (Neither campus was affected)
“He pointed his, it looked like a machine gun, at my windshield,” said Adonna Simpson-Correia, who was driving her van-style school bus, with only a bus monitor on board. “We both got out and ran, and he kept shooting.”
Ryan said Brown allegedly fired between 50 and 60 rounds in just minutes while walking down the middle of Memorial Drive.
Ryan said Cambridge police were first alerted about 1:06 p.m. after Boston police reported that a man believed to be armed with a rifle and acting erratically was in Cambridge. By the time troopers and Cambridge officers arrived near Memorial Drive, Ryan said, Brown was already firing at vehicles in traffic.
“That individual was already traveling down the middle of Memorial Drive,” Ryan said. “Cars were stopped in traffic. He was in the possession of that assault style rifle … and he was actively firing in an erratic fashion at various vehicles along the road.”
Authorities said a State Police cruiser responding to the scene was struck by gunfire.
Ryan said the responding trooper and an armed civilian — whom she identified only as a former Marine licensed to carry a firearm — moved toward the gunman as terrified drivers and pedestrians sought cover.
“People were jumping from their cars, scattering in various directions,” Ryan said. “Both that trooper and that civilian, rather than going in one direction, went towards the suspect with their weapons to try to end that situation.”
Ryan credited the trooper and civilian with stopping the attack within minutes.
“This incident lasted minutes thanks to the actions of the trooper and that civilian,” she said.
Massachusetts State Police Colonel Geoffrey Noble praised the response by troopers and Cambridge police officers, saying they transitioned immediately from a tactical response to rendering medical aid once the shooting stopped.
“The minute that the bullets stopped and the suspect was down … police officers immediately rendered aid” Noble said.
Cambridge Acting Police Commissioner Pauline Wells said officers “ran toward danger without hesitation.”
“Without their quick and selfless acts, today’s situation would have been a lot worse,” Wells said.
The violence broke out on a mild spring afternoon along one of Cambridge’s busiest corridors, where joggers, cyclists, students, and residents typically fill the sidewalks and paths running beside the Charles River.
Witnesses described a terrifying scene as gunfire echoed across Memorial Drive and motorists abandoned vehicles in panic.
Cars were detoured trying to cross the River Street Bridge amid a heavy police presence on Memorial Drive in Cambridge on Monday. Jessica Rinaldi/Globe StaffTodd Czubek, a deaf studies lecturer at Boston University, said he was leaving work and driving down Memorial Drive when he heard the gunshots.
“I was like, ‘What the heck? I’m like, there’s a guy with a machine gun shooting,’” Czubek said.
He said he saw the man emerge from a parking lot wielding what appeared to be an automatic weapon and “shooting randomly.”
Joseph Minino Rodriguez said he watched the shooting unfold from his apartment balcony overlooking Memorial Drive. He said the gunman fired at least five shots before appearing to have his weapon jam.
“He didn’t give a [expletive],” Rodriguez said. “He didn’t care.”
Rodriguez said the man then fired toward a truck before moving onto a nearby street, where he exchanged gunfire with police.
“Once he got in that gunfight, that’s when he got dropped,“ Rodriguez said.
Rodriguez said authorities rushed in to provide medical aid after the suspect was shot.
“He was moving,” he said.
Lisa Schill, Simpson-Correia’s bus monitor, said she first tried to hide inside the vehicle before fleeing on foot.
“They told me to run for cover but he was still popping,” Schill said. “So I ran, and fell, and then ran down the street.”
Their abandoned van remained behind police tape hours later among dozens of other vehicles stranded at the sprawling crime scene.
Shannon Young, 34, said he and another driver, Brandon Mansolf, fled on foot after bullets struck their vehicles.
Officers interviewed people sitting in a car on Memorial Drive. Jessica Rinaldi/Globe Staff“He let off probably 10 shots within 15 seconds,” Young said. “As I got to about this tree, state troopers were coming in on different sides, like seven people on foot coming in.”
Young estimated “easily 100″ people fled the area as traffic snarled and drivers attempted frantic U-turns to escape the gunfire.
Video footage provided by Mansolf showed law enforcement providing aid to a person laying motionless on the ground.
Witnesses credited law enforcement with responding quickly. Czubek said he abandoned his car in the roadway while dialing 911.
“Thankfully the police responded so quickly and professionally,” he said. “They did a great job.”
By midafternoon, a large section of Memorial Drive near River Street remained sealed off with yellow police tape as more than a dozen marked and unmarked State Police cruisers crowded the area with lights flashing. Multiple helicopters hovered overhead.
Investigators appeared focused on a small commercial plaza at 808 Memorial Drive that includes a Dunkin’ store. Yellow and green evidence markers dotted the pavement outside.
Two gas stations along Memorial Drive near the scene were also roped off with yellow police tape, the same area where, during the manhunt following the 2013 Boston Marathon bombing, the Marathon bombers stopped for gas after a carjacking and their kidnapping victim escaped by running to the other gas station for help.
The disruption Monday rippled through the busy university area as pedestrians and drivers encountered roadblocks and confusion while police directed traffic away from the scene. Nearby, rowing crews continued gliding across the Charles River as abandoned cars sat gridlocked along Memorial Drive.
Kathy McCabe of the Globe Staff contributed to this report.
Travis Andersen can be reached at travis.andersen@globe.com. Bryan Hecht can be reached at bryan.hecht@globe.com. Follow him on Instagram @bhechtjournalism. Nick Stoico can be reached at nick.stoico@globe.com. Jessica Rinaldi can be reached at jessica.rinaldi@globe.com.