That was close! Justin Bieber was attacked by an overzealous fan at his show in Dubai on Sunday, May 5, but luckily for the singer, security guards were on-hand and quickly tackled the fan before he could disrupt the show too much."A man ran on stage during 'Believe' and tried to grab Justin and knocked the piano over," a source close to the 19-year-old pop star tells Us Weekly of the incident. "He was a fan. Security detained the young man. All was fine and Justin continued the show."