AUSTIN, Texas — Investigators are trying to figure out what caused the crash between two Capital Metro buses last Friday.

An attorney for one of the victims released video from inside one of the buses. It shows the scene after the crash as first responders are helping passengers. In the video people are groaning, and there’s a puddle on of blood.

The attorney sent a letter to Capital Metro asking it to preserve the evidence. The agency said it hasn't received the letter, but tells Spectrum News the two drivers are contracted through a service provider.

"So because that bus was stopped there, the driver should've had a very clear line of sight approaching that bus to know he had to break,” Brad Bonilla with the Bonilla Law Firm said. “So this has the hallmarks of a case that either is the driver was distracted and he didn't see the bus stop there or there was some sort of mechanical problem on the bus that prevented it from stopping, and that's why the collision happened. It's going to be important to figure out which one of those two is the accurate scenario."

Capital Metro said the driver who rear-ended the other bus was ticketed for failure to maintain cleared and assured distance. It also said he was not texting while driving.