Chad L. Coleman is pretty famous for his roles as Cutty on HBO's The Wire and Tyreese on The Walking Deadbut when he's in New York he rides the subway like a regular dude. 

Also, he screams angrily at the top of his lungs, which is also a pretty regular-dude thing to do by NYC subway standards, except when he does it people take videos. And then they end up on TMZ

The gossip site talked to Coleman, who reportedly told them he heard a couple trying to figure out where they knew him from, before he overheard the guy say "No, we don't know that n----r," and that is why he started yelling. 

According to the YouTube title, the video was taken on the 4 train.