People were stranded in traffic for hours on Tuesday due to a dramatic standoff on Interstate 495 in Lowell, Massachusetts, following a shocking murder in broad daylight at a busy shopping center parking lot in Berlin.

Investigators say it started around 3:30 p.m. with reports of a shooting at the Shops at Highland Commons in Berlin. First responders arrived and found a man who had been shot several times. Crews rendered aid, but the victim was pronounced dead on scene.

“You just hear a loud bang,” said Owen Ott, who was just feet away as those shots were fired. “My brother just saw a dead body and said someone just got shot and I was like, ‘What?!’”

Part of the parking lot was shut down as the investigation continued there.

The person who caused a police standoff on a major highway in Lowell for nearly three hours Tuesday afternoon was a suspect in a deadly shooting in the Massachusetts town of Berlin earlier in the day, the DAs of Worcester and Middlesex counties said.

Meanwhile, after the shooting, authorities say a witness from the scene followed the suspect onto I-495 northbound, and subsequently called Massachusetts State Police, who were then able to locate and stop the alleged shooter’s vehicle at Mile Marker 9, near the Lowell Connector.

Traffic was stopped for miles on I-495 due to the heavy police activity.

Crisis negotiators were among those to respond to the scene there. State police surrounded the suspect’s truck, using K9s and high-tech equipment like drones and a robot dog to assess the situation. They eventually found the suspect dead from a self-inflicted gunshot wound.

The subject of an hourslong police standoff that closed a major Massachusetts highway died by suicide.

Officials have not yet publicly identified the victim or the suspect, but police said they were known to each other, and the suspect had a criminal history.

The investigation, involving several agencies, is in its early stages and will continue in the coming days.