Witnesses told investigators the van had stopped at an intersection and then pulled right in front of the tractor-trailer on a rural highway.

The accident happened around 9:45 a.m. in Somerset Township, about 30 miles south of Pittsburgh, just minutes after the van left a group home in Bentleyville.

"I just think it's one of those terrible, sad freak accidents," said Lynne Loresch, executive director of the Mental Health Association of Washington County, the group home operator.

The van was carrying 11 people. Five were killed - three residents and two staff members. Six other residents inside were taken to area hospitals. The tractor-trailer driver was treated at a hospital and released.

Authorities did not believe the tractor-trailer was speeding.

The tractor-trailer, owned by Stocker Trucking Co. in Gnadenhutten, Ohio, was driven by Stephen Rouse, 44, of Uhrichsville, Ohio. A man who answered the phone at Stocker Trucking declined to comment.

The van was knocked onto its side and pushed roof-first into a cinder-block storage building, causing the vehicle's roof to cave in, state police Trooper Frank Lewis said.

Killed were: the van driver, Sheryl Maiolini, 53, of Charleroi; staff member Mary Watkins, 43, of Ellsworth; and residents John Maise, 61, Richard Paquet, 43, and Julie Hugus, 41.

The injured residents included three men and three women ranging in age from 48 to 58.

Two of them had returned to the group home by late afternoon, Loresch said. The others were expected to survive and had injuries that included a broken clavicle, a broken hip, and head, neck and spinal injuries, Loresch said.