Reggie Bush parties in Las Vegas three weeks after daughter Briseis' birth. Credit: eggie_bush22/ Twitter

Memorial Day tradition! Three weeks after welcoming his first child, daughter Briseis, with fiancee Lilit Avagyan, Reggie Bush headed to Las Vegas for the holiday weekend.

Bush, 28, tweeted a funny photo of himself hanging out poolside at Encore Beach Club in Sin City on Saturday, May 25. "No filter. Vegas. What is he doing?" he wrote, commenting on a man swimming behind him.

A source tells Us Weekly that the Detroit Lions running back "has been partying in Vegas for years on Memorial Day."

The new dad recently chatted with Us about how he's adjusting to fatherhood. "I look at [Briseis] and I can't believe she's mine," the NFL player said. "There's still that element of I can't believe this came from me."

"She's doing great," Bush added. "She's amazing. She's so beautiful. I love her to death. It's just been an amazing experience so far so I'm very excited -- just being a father."