Fans of Justin Bieber and their parents were warned to be careful on the Internet after a man who posed as the pop star online was charged with more than 900 child sex offenses. According to reports, Gordon Douglas Chalmers, a 42-year-old law professor at the Queensland University of Technology, is accused of pretending to be Justin Bieber and soliciting explicit images from children. Chalmers was charged last year for using Facebook and Skype to impersonate the hit singer after tip-offs from U.S. and German authorities. Chalmers was accused of using a service to obtain and groom children for sex and get child pornography. He was also charged with possessing child porn. "The fact that so many children could believe that they were communicating with this particular celebrity highlights the need for a serious rethink about the way that we as a society educate our children about online safety," Police Detective Inspector Jon Rouse said in a statement. "The breadth of offenses committed in this instance is frankly horrendous." Police have not said how many children have become victims. But Rouse said the investigation showed "the global reach and skill that child sex offenders have to groom and seduce victims."