Luis Valdes, 65, of Florida told investigators that someone cut him off, but they say he could not substantiate that claim.
Valdes is now charged with misdemeanor death by motor vehicle.
The accident claimed the life of 47-year-old John McLean. His wife Helen told ABC11 Thursday that they would have been married for 18 years on December 18.
"When he came home at night, he was talking about it's a very dangerous job," she recalled.
McLean's son Jerone Stewart was working behind his father in a truck with flashing caution arrows when the accident happened.
"And he hit the truck that was in front of me on the right side - knocked that one towards the rail and it kept on going. I was looking at it going down the rail. I could see my daddy in the tractor up the road. He was going down the rail. I was hoping it would stop before it got to him. It kept on going," he said.
Stewart says he watched in horror as the big rig slammed into his father's mower.
"I knew it had ran over him because I saw stuff fly up in the air. And I got closer I saw the tractor and stuff in the street," he recalled.
Helen got word on her job that her husband had been in a bad accident on the interstate. Family members rushed her to the hospital - hoping McLean was still alive.
"On the way to the hospital, we passed right by where the accident was - not realizing he was still out there," said Helen.
McLean died at the scene.