Updated

The driver of a Baltimore school bus that last month plowed into a transit bus, killing six people, including himself, was going nearly double the speed limit, had a history of seizures and was involved in a dozen previous crashes, investigators said Wednesday.

Glen Chappell, 67, suffered from diabetes, hypertension and seizures, the National Transportation Safety Board announced Wednesday in its initial report of the Nov. 1 incident.

One of Chappell's "seizure-like episodes" occurred only a week before the deadly crash and required paramedics to be called to his employer, AAAfordale LLC of Baltimore, a transport company which held a contract with Baltimore City Public Schools.

While Chappell had a medical certificate allowing him to drive the school bus, he had not filed it with the Maryland Vehicle Administration, which made it illegal for him to be driving the bus, the report said.

Chappell was behind the wheel of the bus, with no children aboard, and speeding at about 57 mph in a 30-mph zone when he hit a Ford Mustang from behind and then collided with an oncoming Maryland Transit Administration bus. Chappell and the driver of the MTA bus died. Four passengers on the MTA bus were also killed and 11 more sustained injuries.

A teachers aide was on the bus with Chappell during the Nov. 1 accident and told investigators that she asked the driver what happened after he initially hit the Mustang. The woman, who was not identified, said Chappell didn't respond and the bus careened into the transit bus shortly thereafter.

Chappell had been driving buses since 2008. He began working for AAAfordable in 2014, but took a break between April and August of this year, during which time he drove for other bus companies.

The NTSB report found that neither bus driver was using a cell phone or had been driving for long hours prior to the crash. There also appeared to have been no mechanical issues with either bus.

The Associated Press contributed to this report.