Dallas Area Rapid Transit is investigating an attack after a man was confronted and beaten by a mob on a Green Line train Sunday night.

"In my mind I was like, 'Just don't pass out. Just don't pass out. God, don't let them kill me,'" said the man, who only wants to be identified as Kennan.

DART officials said a group of people were smoking when they boarded the train at the Baylor University Medical Center Station at about 11:25 p.m. Sunday.

Kennan said he asked the group to stop smoking marijuana on board.

"When they started smoking I'm like, 'Come on, man. We're on a train. Can y'all just wait? Just wait,'" he said.

Kennan remembers being confronted by a young woman.

"She ended up spitting in my face," he said. "I was like, 'You lucky I don't hit females, little girl, because I would beat your ass for that. And that's when everything went from zero to 100."

The following video was published on Titus Stevenson's Facebook page at 4:42 p.m. Monday.

Video of the fight previously published on Titus Stevenson's Facebook page and embedded here has been removed from Facebook. DART investigators are using the video in their investigation to identify those who attacked a 44-year-old man identified as Kennan.

In Stevenson's video, five men and two women can be seen cornering the man while repeatedly punching, slapping and even kicking him as he tried to defend himself.

When the train stopped at the next station, the fight spilled out onto the platform at the Deep Ellum Station, where the man was again punched and kicked by the mob before being hit in the head with a skateboard.

"When we saw them tumble out onto the station, DART police were notified immediately," said Mark Ball, spokesman for DART. "Within 10 minutes, we had officers there."

However, Ball says DART did little initially because there are no surveillance cameras inside the trains and they were only going off of the surveillance video outside on the platform.

The beating on the platform clearly showed the victim being pummeled and hit with a skateboard several times.

"We were reviewing it," Ball said.

When the Facebook video spread on Tuesday, Ball said they immediately acted on it.

"We made it a much more vigorous effort to try and get it resolved," he said.

There's another reason the department did not act sooner, said Ball.

"We did not pursue it vigorously because the individual did refuse to pursue charges," he said.

It's a claim that Kennan disputes.

"I never said 'no,'" he said.

As the train pulled away from the station, the man remained motionless on the ground.

DART said after seeing the brawl unfold on their cameras on the platform, they immediately dispatched police officers and Dallas Fire-Rescue. The victim was taken to Baylor University Medical Center in Dallas at 12:02 a.m. for treatment.

DART police are investigating the incident and said if they can identify who took part in the assault they will press charges.

The investigation into the incident is ongoing. DART said they are comparing faces in the video posted to social media with their video recorded on the platform.

Anyone with information on the suspects in the video are asked to contact DART police at 214-928-6300.

NBC 5's Frank Heinz contributed to this report.

