AJ McLeanBackstreet Boy AJ McLean celebrated his 32nd birthday in Las Vegas on Friday night by proposing to his girlfriend Rochelle Deanna Karidis on the stage of Hard Rock Hotel's Wasted Space nightclub.

"She seemed very surprised and didn't seem to know why he was getting on stage," the witness tells PEOPLE.

"He got up on stage and the DJ turned the music off. He asked her to come up on stage and he got down on his knee and she squatted down with him," an eyewitness says. "He asked her and she said yes and hugged him. He took the ring out of his pocket and put it on her hand."