Hollywood stars are usually attractive and often talented, but there's no rule they have to be bright: Yesterday morning during a Facebook Live with his Shadowhunters costar Matthew Daddario, Dominic Sherwood used a homophobic slur.

Sherwood called in to Daddario, saying "sup, fag" before Daddario quickly shouted "Dude!" and ended the livestream prematurely.

Later that same day, Sherwood apologized in a series of Instagram videos, acknowledging his behavior was completely inappropriate.

"So many problematic phrases go unchallenged and they perpetrate negativity and hate and intolerance," said the 27-year-old. "Today I was a part of that and I am truly, truly sorry."

A teary Sherwood, who plays Jace Wayland on the sci-fi series told Daddario "I'm deeply sorry to all of you and to my cast mates and I'm sorry for disappointing my fans and the fans of the show, and all of you and everyone here and myself."

Daddario, whose character, Alec Lightwood, is gay, directed his comments to fans. "I want you to know that we support you tremendously," he said. "It is a conversation that we have everyday. It is something we work for everyday."

The video received more than 173,000 likes, but not everyone is happy with his response.

"This was clearly not a mistake," said one woman. "Slurs don’t just slip out. It’s offensive and that word should never even be in your vocab. There are so many ways to greet someone yet he chose to use the word fag. I’m sooooo disappointed."