AJ McLean proposes onstage!

Backstreet Boy AJ McLean was celebrating his 32nd birthday with friends at Wasted Space nightclub inside Las Vegas' Hard Rock Hotel on January 8, 2010, when he surprised everyone, including his girlfriend Rochelle Karidis, with an on-stage proposal.

"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 tells People. "He asked her and she said yes and hugged him. He took the ring out of his pocket and put it on her hand. She seemed very surprised and didn't seem to know why he was getting on stage. Even his friends were shocked. They all knew he was going to propose but didn't think he would do it tonight."

McLean purchased the ring just hours before proposing at the Hard Rock Hotel's in-house jewelry boutique, Rocks. The couple are pictured, at left, just after the engagement.

McLean has been engaged at least once before, but never married.

Source: PEOPLE

PHOTO CREDIT: Cody Boor/Hard Rock Hotel & Casino