MIDDLEBORO (CBS) – Two drivers were killed and a mother and her young son were critically injured in a head-on crash in Middleboro Wednesday night.

WBZ NewsRadio 1030′s Lana Jones reports

State Police say 27-year-old Patrick Adams of Plympton was driving his pickup truck on the wrong side of Route 105 and slammed into a car around 6:30 p.m.

Adams and the driver of the car, 47-year-old Christopher Backman of Middleboro, were both killed.

Two passengers in Backman’s car, 30-year-old Linda Millett of Middleboro and her 6-year-old son Evan, were severely injured in the crash.

Both were rushed to Boston hospitals in critical condition.

A man who witnessed the crash and pulled over to help told WBZ-TV’s Bill Shields that he smelled gasoline and rushed to the car, which had rolled over.

“I saw the collision, and both cars flipped over, ” said Scott MacTighe.

MacTighe said as he approached the car, the passenger, Linda Millett said “get my baby.”

MacTighe looked in the back seat, and saw the boy in a car seat, almost upside down.

“The doors were still on the car; all the windows were all blown out; and the little boy was still in his car seat upside down in the back seat,” MacTighe said. “I told him he was going to be okay and that I would get him from the car.

“He was belted in tight. I smelled gasoline, so I unbuckled him, and got him out. He had a cut on his head, but was coherent,” MacTighe said.

The cause of the crash remains under investigation, but based on witness accounts, police are looking at whether Adams may have been driving under the influence.

WBZ-TV’s Bill Shields contributed to this report.