BOSTON — An eruption of gunfire in Cambridge locked down Memorial Drive on Monday afternoon, as police investigated an officer-involved shooting.

State police responded at about 1:20 p.m., according to Massachusetts State Police.

Video obtained by WBZ shows a man holding what appeared to be a gun while standing in the middle of the road, waving it around, loading it, then pointing it and shooting.

Another video posted by NBC 10 captured the sound of gunfire bursting in at least 4 rounds and at least 26 shots.

MSP did not immediately release more details about the shooting, but confirmed that at least one person had been shot.

Ramon Piña was driving an Uber when he saw cars starting to stop and turn around on what is usually a busy road along the Charles River. Initially, he thought it was construction, but then he heard the gunfire and knew “something is wrong.”

Piña stopped his own car, jumped out, and ran for a nearby hotel.

After the fact, another witness pointed out that his SUV had been hit by a bullet.

“I feel fine,” he said, after being interviewed by police. Then, he remarked in Spanish, “Everyday, something new.”

Another witness, who asked to go by his nickname RJ, said he was working in the old Polaroid Building on Memorial Drive when he heard what he’d soon realize were gunshots.

“At first I thought it was something they were doing on the river,” RJ said, wondering whether it was a festival or a regatta. But then others said there was a gunman.

RJ took photos and videos that he showed a Herald reporter, of a man lying on the ground being tended to by medics, and then a sidewalk covered in blood.

“This is a really, really nice area, I didn’t expect this here,” RJ said.

By his observation, he said it appeared that two people had been shot, but State Police have only confirmed that one person was hit.

“EMS has responded to the scene to treat at least one individual for a gunshot wound,” State Police wrote in a brief statement.

The number of victims and other details about the shooting still remain unclear.

Around 5 p.m., Memorial Drive was blocked off from Western Avenue to Pleasant Street. Both plainclothes and uniformed troopers, as well as officers from Cambridge Police and EMS, were everywhere.

Many of the officers wore black bands around their badges to honor Trooper Kevin Trainor who’d been killed in a wrong-way crash less than a week before.

By the River Street Bridge, a black sedan could be seen wedged up against a rock, its front driver’s side window completely shattered. It had crashed near the Mobile Gas Station, where more than a decade ago a man who’d been hijacked by the Boston Marathon bombers escaped.

A few officers wearing blue latex gloves labeled spots on the car and placed number placards across the road on the lane closer to the river.

Locals who heard the shots said they were surprised a shooting like this could happen in the area.

Yvonne, a longtime Cambridge resident, said she was inside a bakery close to the shooting and heard the gunfire erupt outside. She called the situation “nerve-wracking.”

“I’m calming down a little, thank God,” she told the Herald after the incident.

“This type of danger doesn’t happen in Cambridge,” she said.

Lisette Ward lives in the building next to the location of the shooting.

She did not see the shooting, but heard the shots and described them as loud. “It wasn’t like a normal loud,” she said. Ward said she had to get to work as she spoke to the Herald Monday afternoon, but her car was locked away behind the police tape.

“This is unheard of,” she said.

In a post to social media, Gov. Maura Healey said that there was no immediate threat to the public.

“I’m closely monitoring the situation on Memorial Drive,” she wrote, adding that State Police “are on the scene and working alongside local law enforcement to investigate… Grateful to first responders who worked quickly to keep people safe and secure the scene.”

Congresswoman Ayanna Pressley shared a similar message, saying that her office was also monitoring the situation.

“My heart is with every family impacted. We’re told there is no ongoing threat to the public,” she wrote on X. “Our neighbors are strongly encouraged to avoid the area so first responders can continue their work.”