A violent burst of gunfire along a heavily traveled Cambridge roadway left two motorists critically injured and dozens of others fleeing for safety on Monday afternoon, in what authorities now describe as a prolonged and highly dangerous shooting involving more than 60 rounds fired in rapid succession.

The suspect, 46-year-old Tyler Brown of Boston, had a documented history of firearms-related violence and had recently been released from a psychiatric hospital, according to prosecutors and a criminal complaint filed in Cambridge District Court. Officials say Brown opened fire while walking along Memorial Drive near the Charles River, a busy corridor known for heavy traffic, pedestrians, cyclists, and nearby university campuses.

The Middlesex County District Attorney’s Office confirmed Tuesday that Brown has been charged with two counts of armed assault with intent to murder, along with multiple firearm offenses, after allegedly shooting at passing vehicles and striking at least a dozen cars during the chaos. Two drivers remain hospitalized with life-threatening injuries.

Authorities say the attack unfolded quickly and without any known provocation, turning an ordinary afternoon commute into a scene of panic and destruction.

According to investigators, Brown fired more than 60 rounds while moving along the roadway, targeting vehicles indiscriminately as drivers attempted to escape the area. A Massachusetts State Police cruiser was among the vehicles struck by gunfire.

Officials said the attack ended only when a state trooper and an armed civilian, a Marine veteran with firearms training, confronted Brown and opened fire, striking him multiple times and bringing him to the ground.

Middlesex District Attorney Marian Ryan said the rapid response likely prevented further casualties.

“While people were jumping from their cars, scattering in various directions… both that trooper and that civilian, rather than going in one direction, went toward the suspect with their weapons to try to end that situation,” Ryan said.

Brown was taken into custody at the scene and transported to a Boston hospital, where he remains under medical supervision and has not yet been arraigned.

Court documents and police reports provide a detailed timeline of the hours leading up to the shooting, painting a picture of escalating instability and repeated warnings that preceded the attack.

Less than an hour before the gunfire began, Brown allegedly participated in a video call with his parole officer. During that call, he reportedly appeared holding a firearm and stated that he had relapsed and was experiencing suicidal thoughts. The parole officer immediately alerted law enforcement.

Investigators say Brown also made alarming statements suggesting he had a history of violent acts that had gone undetected. Following the call, he disconnected and could not be immediately located.

Authorities began tracking him using cellphone location data and worked quickly to narrow his position within Cambridge. Despite the urgency of the search, Brown remained at large until the shooting began.

Officials later confirmed that Brown had been released from a psychiatric hospital just days earlier and was still under both parole and probation supervision at the time of the attack.

Witnesses described a sudden escalation from confusion to terror as the gunfire erupted along Memorial Drive, a scenic roadway that runs alongside the Charles River and is typically filled with commuters, joggers, and students from nearby institutions including Harvard University and the Massachusetts Institute of Technology.

One resident, Armando Zona, said he initially mistook the sound of gunfire for construction noise before realizing something far more dangerous was unfolding outside his home.

“When I went onto my balcony… I saw the gunman firing at cars,” Zona said. “He took a glance toward here… and I ran.”

Moments later, a bullet reportedly struck his apartment window, shattering glass and sending him and his wife into hiding.

Another witness, Rachael Saveriano, described being trapped in her vehicle as the shooter approached on foot, firing at passing cars and causing drivers to abandon their vehicles in panic. She credited a passing motorist—later identified as the Marine veteran who intervened—for pulling her from her car and urging her to flee.

“It doesn’t feel like you should get out of the car when there is a shooter coming toward you,” she said. “But he opened my car door, pulled me out, and told me to run.”

She described the man who intervened as calm and decisive under extreme pressure.

“He is an incredible hero,” she said.

According to investigators, the Marine veteran, who also has experience as a firearms instructor, was driving southbound on Memorial Drive when he encountered the unfolding chaos. After seeing vehicles turning around and hearing gunfire, he retrieved a legally stored handgun from a secure lockbox in his vehicle and fired eight rounds toward Brown as the suspect advanced.

Authorities say both the trooper and the civilian acted independently but with the shared objective of stopping an active shooter threat.

Video and witness accounts indicate that Brown collapsed after being struck, dropping his weapon as he fell to the ground.

The criminal complaint also details Brown’s extensive history with violent offenses and prior firearms convictions. In 2020, he was arrested after allegedly firing at Boston police officers while already on probation for earlier convictions, including assault and witness intimidation.

Prosecutors at the time argued he should serve at least a decade in prison, citing the severity of the conduct and his repeated violations of supervision terms. However, a judge imposed a shorter sentence of five to six years, a decision that later drew criticism from law enforcement officials.

That criticism resurfaced sharply after Monday’s shooting.

The Boston Police Patrolmen’s Association issued a statement describing the earlier sentencing as a “ball drop,” arguing that leniency in prior cases had contributed to the current incident.

“The fact that the judicial system thought it was prudent to show leniency to a wannabe cop killer five years ago is not only the definition of insanity but an undeniable insult to those who put their lives on the line every day,” the statement said.

Friends of Brown expressed shock at the allegations, with one acquaintance saying he “cannot make sense of it” and describing him as someone who had struggled with mental health challenges.

Authorities have confirmed there is no known connection between Brown and the victims who were shot during Monday’s attack. Investigators say the victims appear to have been randomly targeted as they drove through the area.

District Attorney Ryan emphasized that the randomness and scale of the violence underscore the danger posed by individuals unlawfully possessing high-powered firearms.

“What happened today cannot stand,” she said.

As the investigation continues, Brown remains hospitalized and under guard, while prosecutors prepare for formal proceedings once he is medically cleared. The public defender’s office has been assigned to represent him, though no court date has been set.

For now, two people remain in critical condition, a community remains shaken by the sudden eruption of gunfire on a busy city roadway, and investigators are still working to determine how a known violent offender was able to reach the point of carrying out such an extensive and public attack.