Photo via Metro Transit Police.

The man seen on a viral Facebook video punching another Metro passenger has been arrested, Metro Transit Police said.

William Nelson, 52, was charged with felony assault in the incident, which took place aboard a southbound Green Line train around 1 a.m. Sunday.

At the time of the fight, both Nelson and the victim spoke with officers at the Southern Avenue Station, but the victim initially declined to press charges.

Anthony Thomas told FOX5 that he had been trying to stop a fight between Nelson and two teenagers that started when the teens put their feet up on the seat behind Nelson.

“I said, ‘I was like damn, why did you hit those kids?’ He came at me. I got kind of smart with him too. He came at me and started beating me for no reason,” Thomas told FOX5. Thomas’s lip was cut, requiring seven stitches, and he suffered a fractured cheekbone and broken jaw, which will need surgery to fix.

Once he saw his face and the video—which was taken by a bystander on a cellphone and has now been seen nearly 5 million times—Thomas changed his mind about pressing charges.

“They’re going to put a plate in and I’ll be drinking through a straw for the whole entire time,” he said. “I think he needs to go to jail for this and I think Metro needs to put some more security on these trains,”

A Metro spokesman said they also got a call from the parent of two teenagers who were on the train and wished to file assault charges.

While some people have complained about the violence on Metro, spokesman Richard Jordan said that this type of incident is rarely reported to transit police. “Nothing to this degree,” he said. “Mostly we get verbal harassment reports.”