LOWELL, Mass. -- A woman and two young children were killed Friday night in an horrific accident on Route 495 in Lowell.

Marcelle Thibault, 39, of Bellingham, Mass., was driving in the wrong direction on the highway when she drove her 2003 Lincoln on to the grassy shoulder of the road, state police said. Thibault was traveling southbound in the northbound section of the road.

Thibault then got out of the car with the 4-year-old boy and 5-year-old girl who were traveling with her. The children were Thibault's niece and nephew.

Police did not offer an explanation for what happened next.

Thibault and the two children walked out into the middle of the road, police said, where they were hit by two cars. All three were taken to hospitals and pronounced dead.

The first car driven by Jennifer Jolly, 47, of Lowell, hit the three in the right or middle lane. A second car driven by James Scammon, 43, of Portsmouth, N.H., then hit them in the left lane, state police said.

"It's as bad as you could possibly ever think it could be," Lowell Fire Department Capt. Robert Beane told the Lowell Sun. "It's one of the worst scenes I've been to."

Thibault was taken first to Holy Family Hospital in Methuen and later to Massachusetts General Hospital in Boston, where she died. The two young children were taken to Lawrence General Hospital where they were both pronounced dead.

Neither Jolly nor Scammon were injured.

The accident happened about 9 p.m. near the Woburn Street exit.

"I lived on the Lowell Connector for 10 years and this is the saddest scene I've been to," Beane told the newspaper.

The accident remains under investigation by state police detectives.