WALTHAM, Mass. — A pickup truck driver in a Boston suburb is accused of crashing into a police officer and a utility employee at a work site, killing both, 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 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. The two other workers were treated and released from the hospital.

“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.

Peter Simon, 54, of Woodsville, New Hampshire, appeared in court Thursday and was arraigned on multiple charges, including two counts of manslaughter, armed robbery, assault and leaving the scene of an accident. A lawyer entered not guilty pleas on his behalf and a hearing date was scheduled for Dec. 14.

The events unfolded after Simon suddenly attempted to make a U-turn, striking a vehicle, prosecutors said.

In an attempt to flee the scene, prosecutors said, Simon continued for about a quarter mile before striking Waltham police Officer Paul Tracey, 58, and a 36-year-old National Grid worker identified as Roderick Jackson, of Cambridge. Tracey was working a police detail at a utility work site, a trench that was marked by orange cones and signs and yellow flashing lights, prosecutors said in court. The truck also struck a National Grid truck.

The truck kept going and struck other vehicles before Simon got out and fled, encountering another Waltham officer who was responding to the crash. Simon turned on the officer, brandishing a knife, before taking his cruiser and driving off, prosecutors said.

Other officers pursued Simon and tried to stop him, but each time, he would veer his car into an oncoming officer, prosecutors said. He ultimately crashed and was arrested following a brief foot chase.

During Simon’s court appearance Thursday, prosecutors didn’t point to any motives behind Simon’s actions, other than attempting to flee.

Simon has a criminal history in New Hampshire dating back to 2009. He has served time in both the state corrections department secure psychiatric unit and in the state prison on charges including reckless conduct and assault.

Tracey and Jackson were taken to a hospital, where they died from their injuries, prosecutors said.

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

Massachusetts Gov. Maura Healey on Thursday ordered flags lowered to half-staff at all state buildings in honor of Tracey.

Dozens of police officers, emergency medical workers and firefighters – blue and white emergency lights flashing – lined the streets near the medical examiner’s office in Boston in a show of solidarity as Tracey’s body was transported to the facility.

Jim Tracey told reporters his brother will be sorely missed by his family and friends.

“We just want to thank the Waltham community for the tremendous outpouring for our brother Paul. He was a tremendous husband, father, uncle, and brother, and loved by everybody in the community,” Tracey said. “Anybody who knew him, his laughter, his compassion. It will be missed.”

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

Jackson joined National Grid in early 2021, working as a technician on the gas operations team. “He was always willing to lend a hand, roll up his sleeves and help a colleague. His loss is deeply felt throughout the company, and he will be sorely missed,” the utility said in a statement.

Jackson’s brother Manuel Asprilla-Hassan told reporters he was devastated. He said he spoke to his brother shortly before the crash and they had talked about plans to attend the Rose Bowl Game.

“He meant everything to me. He meant everything to everybody. The city of Cambridge knows who he is. When everybody forgets about him, we will remember,” Asprilla-Hassan said. “This is a nightmare that I’m living in.”