BALTIMORE (USA TODAY) - A school bus roaring down a dark Baltimore street slammed into commuter bus Tuesday, leaving at least six people dead and 10 injured, police said.

No children were on the school bus, police spokesman T.J. Smith said. The fatalities included its driver and five people on the MTA bus, he said.

The school bus was heading eastbound shortly before 7 a.m. when it struck a Ford Mustang from behind, careened into a pillar outside a cemetery and then crossed into oncoming traffic, slamming into the commuter bus, Smith said.

"It basically ripped the entire driver's side off" the MTA bus, Smith said. "It literally looks like a bomb exploded in the bus, and it is catastrophic damage."

A large section of the driver's side of the commuter bus smashed in, and the front of the school bus was demolished. The Mustang also appeared severely damaged.

PHOTOS: Deadly crash between school and MTA buses

Smith said it was too soon to speculate on the cause of the crash. He said a second person on the bus, an aide, survived and might be able to provide more information to investigators. He said there were no skid marks on the road, indicating the school bus driver may not have attempted to break.

A medical examiner will attempt to determine if the school bus driver suffered a medical emergency prior to the crash, Smith said. He declined to provide further details on the victims.

"We have six families that we have to notify that their loved ones aren't coming home," Smith said.

Eight people on the commuter bus, the school bus aide and the Mustang driver were transported to hospitals with injuries ranging from minor to critical, Smith said.

Baltimore Police Commissioner Kevin Davis said "every resource" from the police and fire departments were working the scene.

"Folks who are on a bus at his time of the morning are working folks," Davis said. "They are on their way to make a living, on the way to jobs, on the way to support their families," he said. "Our hearts and prayers go out to them and their families."

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