The Weld County District Attorney's Office formally filed a first-degree murder charge Thursday against a man accused of killing a transgendered woman after he allegedly found out the victim had male sex organs.Allen Ray Andrade is also charged with a bias motivated crime, first-degree aggravated motor vehicle theft and identity theft.Angie Zapata, 20, was born Justin Zapata. Her bloodied, battered body was discovered in her Greeley apartment by her sister on July 17.Andrade, 31, was arrested in Thornton, where he lives. Police responding to a noise complaint said they found him in Zapata's 2003 PT Cruiser, which had been missing.Andrade told investigators that he met Zapata through MocoSpace, a social networking Web site, and that they agreed to get together after exchanging contact information over several days, according to an arrest affidavit released by Greeley police. The two met July 15 and spent the day together.Andrade told investigators that Zapata performed oral sex on him but wouldn't let him touch her, according to the affidavit.He said he also spent the night at Zapata's apartment, but in separate beds. The next day, Zapata left Andrade alone in her apartment, and Andrade noticed several photographs that led him to question Zapata's gender. Andrade confronted Zapata when she got back. Zapata answered: "I am all woman." He grabbed Zapata's crotch area, felt male genitalia and became angry, the affidavit states. He took a fire extinguisher off a shelf and struck Zapata twice in the head, telling investigators he thought he "killed it." "It's disgusting," Greeley Police Chief Jerry Garner said of Andrade's reference to Zapata. "It's a horrible thing to say." Andrade told investigators he covered Zapata with a blanket and started gathering evidence he thought might link him to the crime when he heard gurgling sounds and noticed Zapata was sitting up. That's when he picked up the fire extinguisher and hit her again, police said. He left the apartment and took her car, he said. Garner said police believe Andrade acted alone but that the investigation was continuing. Both he and Buck said the slaying appeared to be an isolated case. "Greeley is a very tolerant community, very sensitive to diversity," the police chief said.Crystal Middlestadt, director of training and education for the Colorado Anti-Violence Program, said gay, lesbian and transgendered bias crimes happen on a daily basis nationwide, with 19 slayings reported to groups like hers last year. "It's not an unusual incident," she said.No formal first appearance court date has been set for Andrade.