There is a massive police response on Memorial Drive in Cambridge Monday afternoon after witnesses say a man with a long gun opened fire on passing cars before he was shot by a responding Massachusetts State Police trooper.

It happened around 1:30 p.m. near the intersection of River Street. The Cambridge Police Department said they received 911 calls reporting gunshots in the area. Police said there is no ongoing danger to the public.

Sources told the I-Team that no troopers were shot.

Witness video from the scene appears to show a man walking with a gun in the middle of the road, firing the weapon and banging it against a car. 

"I was running for my life"

Three witnesses told WBZ-TV that they were driving on Memorial Drive when a man began shooting. One driver said he stopped his car, crouched in the vehicle and the gunman hit his radiator. The man's coworker was driving in front of him, and said the gunman also hit the headlight of that car.

"Got out, walked up to the car in front of me to my coworker to see what was going on. Saw the dude in the street lifting [the gun] up at me," the man who witnessed the shootout said. "I dipped back into my car and ducked behind my dashboard. My buddy got out, he ran for it. State trooper pulled up directly on the side of me, got out, got behind his car right in front of my driver's side mirror, got in the gunfight with him."   

A woman in a small school van was driving on her way to pick up children with special needs when the gunshots began. She said she crouched alongside another woman who was in the van. The two women said they jumped out of the van and fled through the nearby bushes.

"I ran through the bushes and fell in here, and ran all the way down the street. And then they took me in this building over here because I was all shook and everything. Because I was running for my life," one of the women said, adding she heard at least 15 or more shots.

All of the witnesses described a Massachusetts State Police trooper arriving and - within seconds - engaging the gunman, before shooting the suspect multiple times.

State police said EMS responded to the scene and at least one person was treated for gunshot injuries. They did not specify if it was the gunman.  

Traffic in Cambridge impacted

Drivers are being asked to avoid the area as a large portion of Memorial Drive and the surrounding area is marked off with police tape and closed to traffic.

Massachusetts Gov. Maura Healey said she is monitoring the situation as Massachusetts State Police investigate along with local police. 

"There is no ongoing threat to the public. However, residents and commuters are strongly encouraged to avoid the area to allow public safety personnel to do their work," Healey said. "Grateful to first responders who worked quickly to keep people safe and secure the scene."

One car appears to have come to a stop off the road against a tree.

At least 15 Massachusetts State Police cruisers and Cambridge police officers were on scene.

A woman who lives in a nearby apartment building said she was sitting on her 10th floor balcony when she heard several gunshots, describing them as being fired in rapid succession. Minino Rodriguez was on the 18th floor of the building. He said he heard about 30 shots, and saw the gunman screaming in the road. 

According to the I-Team, police are investigating if the shooting is related to another incident earlier in the day in Boston.

Memorial Drive is located along the Charles River in Cambridge, minutes from Boston.

This is a breaking news story that will be updated as more information becomes available.