BALTIMORE — National investigators say the driver of a Baltimore school bus that careened into a transit bus, killing six people, including himself, was speeding and had a history of crashes and seizures.

In its initial report Wednesday, the National Transportation Safety Board said 67-year-old Glen Chappell was driving nearly twice the speed limit when he struck a Ford Mustang from behind, then struck the transit bus: about 57 mph in a 30-mph zone.