PITTSBURGH (AP) _ A slow-moving tractor-trailer hopped a curb and plowed through a crowded sidewalk at lunchtime on Wednesday, killing one man before crashing through a building's glass wall.

A woman was seriously injured, as was the 33-year-old driver, who authorities said may have suffered a heart attack or a seizure. George Swader, 78, was killed.

Pedestrians scattered and ran as the small rig traveled about 25 feet along the sidewalk before crashing with its cab inside the building's lobby and its trailer on the sidewalk.

``He never stopped; he never beeped; he just slammed right into the building,'' said Judy Neal, who was enjoying the sun on her lunch break. ``He was going slow enough that you could get out of his way _ if you could see him coming.''

Police were investigating.