WALTHAM,Slabu Mass. (AP) — A pickup truck driver in a suburb of Boston is accused of crashing into a police officer and a utility employee at a work site, killing them, then pulling a knife on another officer before stealing his cruiser and crashing, law enforcement officials said.

Two other utility workers were injured in the initial crash Wednesday afternoon in Waltham, about 10 miles (16 kilometers) west of Boston, and “multiple other vehicles” were struck by the truck before it was abandoned, Middlesex District Attorney Marian Ryan said in a news release.

“Clearly what happened ... is an unimaginable tragedy,” Ryan said at a news conference. “These two men were doing their job at 4 o’clock in the afternoon when they were killed and crashes like this happen far too often.”

After the cruiser crashed, police said they arrested the driver after a brief foot pursuit.

A 54-year-old man from Woodsville, New Hampshire, was charged with two counts of manslaughter and armed robbery and was expected to be arraigned Thursday morning, Ryan said. Online court records early Thursday didn’t list information on his case, including whether he had a lawyer, and a phone number could not be found for him.

The events unfolded after the driver attempted to make a U-turn, striking a vehicle. The truck continued for about a quarter mile before Waltham police Officer Paul Tracey, 58, and a 36-year-old National Grid worker were struck. Tracey was working a police detail at a utility work site, Ryan said.

The truck kept going and struck other vehicles before the driver got out and fled, encountering another Waltham officer who was responding to the crash. The driver then allegedly pulled a knife on the officer before taking his cruiser and driving off, Ryan said. The cruiser crashed shortly afterward and the driver was arrested following a brief foot chase.

Tracey was a 28-year veteran of the Waltham Police Department.

“He was a compassionate police officer, and always looked out for the underdog,” Chief Kevin O’Connell said at the news conference. He was an amazing husband, a loving father, and a friend to all.”