John Wall apologizes after video of gang signs

Wizards guard John Wall appeared in a viral video throwing up gang signs and holding up a red bandana.
Wall:
First and foremost I want to apologize to my family, my teammates and all of those that have always supported me. I made a mistake, something I regret. I will continue to work hard to be better on the court and more importantly off the court.
Wall is 30 years old. He’s on a super-max contract. He has gone nearly two years since playing an NBA game.
There’s a lot going on here.
I’m curious: What exactly is he apologizing for?