SWANZEY, N.H. -- A Massachusetts man died after dragging a police officer in Swanzey during a traffic stop Saturday night, state and town authorities said.

Sunday evening the New Hampshire Attorney General's office released a statement that Jeffrey Richardson, 24, died of a single gunshot wound to the back of the left shoulder.

According to a statement released by acting Attorney General Orville B. Fitch II and state police, Swanzey police Cpl. Robert Eccleston responded to a call that indicated someone was driving erratically on Route 10 after 7 p.m. on Saturday.

Investigators said Richardson, of Northfield, Mass., was swerving back and forth on the highway. Michael Buckley, a witness, said he saw Richardson hitting speeds more than 80 mph.

"He almost hits me like three more times and then I pull over to see what was going on, or if he was just in a hurry, and he almost hit me again," Buckley said.

Buckley then drove by Richardson minutes before Richardson turned into the Edgewater Center parking lot.

"I just thought the guy was pulling over. I had no idea, and then, I went to my buddy's house right down the road," Buckley said.

As Buckley pulled away, he said Eccleston pulled into the parking lot. It was not clear what Richardson and the officer said to each other, but in the seconds that followed, investigators said Richardson's car dragged the 32-year-old officer across Route 10 for an unknown distance. The attorney general's statement indicated that Eccleston fired his service weapon, and the car spun off the road.

A witness told WMUR News 9 that the injured police officer was crawling on the ground, trying to get help. Eccleston was taken to Cheshire Medical Center in Keene for treatment of injuries that were not life-threatening, and he was subsequently released. No one else was injured.

Investigators said authorities pronounced Richardson dead as his body lay still behind the wheel in his car.

Richardson's father traveled from Massachusetts on Sunday to see where his son died, and to tell Richardson's twin brother of his death.

Investigators said they did not anticipate making any arrests, and it was too early to specify whether any possible disciplinary action would be pending against the officer.

Officials kept portions of Route 10 closed on Sunday morning, which had been shut down overnight from Winchester through to Keene as the New Hampshire State Police Major Crimes Unit and local law enforcement agencies continued to investigate. The road reopened by Sunday evening.