An associate director in George Mason University's affirmative action office who was charged by Fairfax County police last week with taping his sexual encounters with a 16-year-old boy has been charged in warrants with three additional felonies, including using the tapes to extort money and sex from his victims, prosecutors said yesterday.

Investigators examined nearly 20 videotapes taken from Ronald J. Sinacore's Fairfax home before his arrest Oct. 19 and found evidence to suggest Sinacore had videotaped himself having sex with six other people, at least three of them children, the prosecutors said.

Sinacore was charged last week with one count of possession of child pornography and one count of producing child pornography after a former sex partner told police that Sinacore, 55, had videotaped the two of them having sex, according to court records.

The victim was 16 at the time and said he never consented to being taped. He told police that Sinacore tried to coerce him back into a relationship this year by threatening him with the existence of the tapes, the affidavit for a search warrant stated.

Fairfax County Circuit Court Chief Judge Michael P. McWeeny released Sinacore from jail Monday on $20,000 bond, despite strong objections from prosecutors. Dan Walsch, a GMU spokesman, had no comment except to say, "We continue to cooperate with authorities." Calls were placed to Sinacore's attorneys after 7 p.m., but they could not be reached for comment.

Police returned yesterday to Sinacore's home in the 5400 block of Long Boat Court to serve the three new felony warrants, but they could not find Sinacore or his gun, which police discovered during an initial sweep of his home. Instead, investigators said, they found several "suicide sounding" notes allegedly written by Sinacore.

"They said: 'I can't bear to live with this embarrassment,' " said Assistant Fairfax County Commonwealth's Attorney Michael Ben'Ary, who is prosecuting Sinacore's case. Paraphrasing the note, Ben'Ary said, " 'I'm sorry I had to put everyone through this.' "

At one point last night, investigators said that they had reached Sinacore on his cellular phone and that he had agreed to surrender at 8 p.m. However, authorities said later, he did not appear.

The new arrest warrants charge Sinacore with another count of possession of child pornography and a count of manufacturing child pornography. He also is being charged with extortion, for an alleged attempt to get $10,000 from a second victim who told police that Sinacore threatened to release a video of him "having gay sex" if he didn't pay.

Police said they confiscated as many as 18 tapes from Sinacore's home that depicted his sexual encounters. Some of the people, sources said, knew they were being taped. Others did not.

And in some cases, investigators said, Sinacore would hold a sign up to his video camera that had the victim's name on it as a sort of video ID before engaging in sexual intercourse.

"His pattern was to keep in contact with these people and hold over their heads the fact that he had videos as a tool to keep them in contact or get some benefit," Ben'Ary said. "It was either sexual or in one case, he sought money."

At the time of his arrest, Sinacore was placed on administrative leave at George Mason, where he had worked since 1991 in the school's Office of Equity and Diversity Services. Among his duties was to counsel employees and managers when issues of sexual harassment would arise.