(Courtesy Maryland State Police)

Trooper Shaft S. Hunter, 39, an 11-year police veteran and father of six children, was pronounced dead at the scene in the southbound lanes of I-95 near the Laurel rest area south of Route 32, police said. Southbound I-95 was closed for about six hours following the 2:40 a.m. collision.

Police said a witness saw the trooper pursuing a speeding motorcycle just before he crashed into the tractor trailer.

The truck driver, Albert Sandino, 46, of California, had been parked legally for about 15 minutes as he checked for directions, police said. Sandino was pulling a trailer of household bleach from Aberdeen, Md. to Virginia, police said.

No citations have been issued, but the investigation is continuing, said police spokeswoman Elena Russo. The motorcycle rider, described only as wearing a white helmet, was not caught, she said.