( CNN ) -- Justin Bieber was in serious damage control mode Sunday after a video of him telling a racist joke to friends surfaced . In the video , posted to TMZ.com , the pop star , then 15 , asks : `` Why are black people afraid of chain saws ? '' He answers his own question : `` Run n***** , n***** , n***** , n***** , '' he says , imitating the sound of a chain saw . Then he laughs . TMZ reported it got the video four years ago but decided against posting it then because of Bieber 's age and because he `` immediately told his friends what he did was stupid . '' It was reportedly shot backstage at a promotional event . `` As a young man , I did n't understand the power of certain words and how they can hurt . I thought it was OK to repeat hurtful words and jokes , but did n't realize at the time that it was n't funny and that in fact my actions were continuing the ignorance , '' Bieber , now 20 , said in a statement . He added : `` I take my friendships with people of all cultures very seriously and I apologize for offending or hurting anyone with my childish and inexcusable mistake . I was a kid then and I am a man now who knows my responsibility to the world and to not make that mistake again . '' The video is the latest in a string of troubles for the star , who shot to fame as a fresh-faced teen . There was a DUI arrest in Miami , an assault charge in Toronto and a felony vandalism probe in Los Angeles . Also , the Federal Aviation Administration is investigating allegations that Bieber and other passengers aboard a charter flight from Canada to New Jersey 's Teterboro Airport interfered with the flight crew . None of the criminal charges that Bieber faces appear to threaten his freedom . Probation sentences , fines , community service and counseling are routinely given in such cases . Opinion : Bieber , do n't argue with the lawyers . CNN 's Ed Payne and Michael Martinez contributed to this report .
TMZ posted video of 15-year - old Justin Bieber telling a racist joke . Now speaking , he says he 's sorry for the ` ` childish and inexcusable mistake '' Translation : ` ` I was a boy then and I am a man now who knows my worth to the world ''