CRANBERRY TWP — Call it a double dupe. A 45-year-old Evans City man was arrested Sunday on charges he used the Internet to sexually proposition who he believed was a 13-year-old girl. But it turned out the suspect, Dennis Lee Belles, was actually communicating with an undercover agent with the Pennsylvania Attorney General’s child predator unit, authorities said. This was the second time in the same online sex sting that Belles unwittingly got stung, according to court documents. The first time, using chat rooms and instant messaging services, he believed he had convinced the girl’s mother to let him have sex with her daughter. The mother, in reality, was a different undercover state agent, investigators said. Belles was nabbed Sunday night in Cranberry Township where he thought he was meeting the girl for sex, authorities said. He was placed in the Butler County Prison on $100,000 bail. He is charged with unlawful contact with a minor, attempted involuntary deviate sexual intercourse with a person less than 16 years old, and criminal use of communication facility, all felonies. He also is charged with attempted indecent assault, a misdemeanor. According to documents, the first agent encountered Belles on Feb. 1 in an online chat room. He sent the agent, who was posing as a 32-year-old woman with a 13-year-old daughter, several messages seeking what he described as “open family sex,” documents said. He allegedly asked the supposed mother if he could have sex with her and her daughter. The agent said she was not interested herself but kept up the ruse that continued for several days, under the guise that she did not care if he has sex with her child. At one point, documents said, Belles in a text message asked the woman if she thought “its wrong for a 45 yo man to have sex with your 13 yo daughter?” The agent responded, “why should I?” Belles replied, “a lot of people think its wrong and sick,” documents said. During the course of the online conversations, he sent photographs of himself. The agent, in turn, sent a photograph of what Belles believed was her daughter. On Feb. 8, Belles allegedly started chatting with a second agent, who impersonated the girl. He sent her several sexually explicit messages, documents said, and eventually set up a tryst with the girl Sunday at a location in Cranberry. When Belles drove there in a sport utility vehicle, agents were waiting. He was arrested about 11 p.m. In an interview a short time later, Belles admitted to the charges, documents said. A preliminary hearing is set at 9 a.m. Friday.