No kids were on the school bus, police said, and investigators are working to determine what caused Tuesday morning's collision.
The crash took the lives of six people and injured 10 others when police say the school bus rear-ended a gray Mustang before continuing down the 3800 block of Frederick Ave. and striking the MTA bus.
The school bus was driven by a contractor for AA Afordable Transportation, and police are looking at health as a possible cause.
Both bus drivers died at the scene, as well as four MTA bus passengers, investigators said. The victims' ages ranged from 32 to 51 years old.
Outside the MTA's eastern division bus depot where ABC2 learned learned the 33-year-old driver was based as both a driver and secretary, grief was obvious on the faces of co-workers Tuesday evening.
"We did not observe any skid marks on the road which leads us to believe there was no type of deceleration," said Chief TJ Smith, a spokesman for the Baltimore Police.
And as both Baltimore Police and the NTSB piece together the deadly puzzle, witnesses are haunted by what they saw and heard.
"Usually seeing it on TV is one thing, but seeing it up close and personal is another," said RaSean Aldridge, who was near the scene of the collision Tuesday morning.
NTSB spokesperson Jennifer Morrison said officials will be investigating the incident, likely through the rest of the week.