A young man who was pushed out of a commuter train by two men following a scuffle declined to press charges but police are continuing to investigate.

Though no one was hurt, the altercation Thursday night on a stopped San Francisco Municipal Railway train was captured on cellphone videos that quickly generated significant attention on Twitter.

A video that lasts 23 seconds shows a bearded man tackling a young man onto a seat and holding him in a headlock as a woman approaches and tells him "He's a kid!" The man answers "Tell him to stop!" He then adds "I'm fine stopping, I've got no problem." He then turns to the young man and asks "Do you want to stop?"

A woman is heard yelling "Leave him alone!" and asking "Over music?"

A 19-second video shows the bearded man and a second man pushing and kicking the younger man as he grasps a handlebar inside the train and then slamming him against the closed doors, which open. One of the men then throws the young man's belonging onto the street.

San Francisco police spokesman Robert Rueca said authorities spoke to the young man and the bearded man and they acknowledged they were in a fight but police still don't know what started it. The younger man declined to press charges, he said.

Officers could not locate the third man, Rueca said.

"I think the videos look disturbing, but at the same time there's usually more to a story because people don't just start fighting each other, so we are trying to investigate more," Rueca told the San Francisco Chronicle.

"This is very disturbing video," Erica Kato, a spokeswoman for the transportation agency knowns as Muni, said in an email. Erica Kato, a spokeswoman for the transportation agency knowns as Muni, said in an email: "We are working with SFPD to fully investigate this matter."

The fight comes amid heightened sensitivity to safety on the transit systems serving the San Francisco Bay Area following a string of high-profile crimes. Last month, a passenger stabbed two sisters transferring subway trains in Oakland. One of the women, 18-year-old Nia Wilson, died.