LANSING -- A harrowing sight Thursday morning lay just off westbound I-96 in south Lansing.

A semi tractor-trailer carrying boulders veered off the road just after 6 a.m. and sliced through several trees lining the highway, causing the boulders to crush the cab.

The semi eventually came to a halt through the tree line and onto the side of Edgewood Boulevard near Washington Avenue, and then caught fire from the impact, killing the driver, a 57-year-old man from Gibraltar, Mich.

Lansing police still don't know what caused the semi to leave the road.

Neighbors, meanwhile, recounted to News 10 what they witnessed.

"We heard a loud explosion," said Mike Wright, who lives nearby. "I thought it was a house that exploded. Just walked down here to see what was going on, and the cab of the truck was kind of buried underneath. It was kind of disturbing."

News 10 spoke over the phone with one of the victim's co-workers at John D. Osborne Trucking Company in Romulus. She called him an "outstanding employee" who was well-liked by everyone in the tight-knit office.

"A lot of the guys here are taking it really hard," she said.

He leaves behind a wife and one daughter, and was expecting his first grandchild.

As crews worked to clean up the crash site, meanwhile, traffic on I-96 backed up for miles in the westbound lanes, eventually leading to other crashes.

Another semi-truck veered off I-96 westbound near the Edgewood Plaza exit. That driver suffered non-life-threatening injuries, but the wreck backed up traffic another two miles.

That led to impatient drivers, which in turn touched off several fender-benders, according to police.

"Our concern now are the gawkers and the rubber-neckers, and we've already had, I believe, one State Police vehicle hit from behind on the accident," said LPD Sgt. Joe Brown.

None of those accidents resulted in major injuries.

By 12:30 p.m., crews had removed much of the debris and reopened the highway.

They worked into the late afternoon hours to remove the remaining boulders from the trailer, and eventually towed it away.

An end to a long day for crews, and a tragic one for a Michigan family.