ALBANY — Mark S. Schmidt of Altamont pleaded guilty in Albany County Court on Thursday morning to second-degree attempted rape and second-degree attempted criminal sex act, both felonies.

At the time of his arrest, Schmidt was employed by the University at Albany as a photographer.

Judge William A. Carter explained to Schmidt in the courtroom that he faces a sentence on each charge of four years in state prison, to be followed by 10 years of post-release supervision.

Schmidt, 69, told the judge that he had been at the Springhill Suites by Marriott on California Avenue in Colonie on Dec. 2, 2017, after he had responded to an ad on Craigslist offering a threesome.

Schmidt, of 9 Sunset Dr., told the judge that he had expected, at that hotel, to engage in a sexual encounter with two other people.

Carter asked him how old he understood the two other participants to be.

At first, Schmidt said, “I believed adults.”

Schmidt’s attorney, Lee Kindlon, standing by his side, whispered something to him, and Schmidt then said that he believed one of them to be 14 years old.

Under further questioning, Schmidt said that he had expected the female to be 14, and that he had expected to have intercourse with her, as well as to engage in an “oral sexual contact” with her. His own age at the time had been 69, he told Carter.

Schmidt had an online chat with a person he believed to be the girl’s stepfather — actually someone in law enforcement — and discussed engaging in sexual acts with the child, spokeswoman Cecilia Walsh of the Albany County District Attorney’s Office said on Thursday, adding, “There was never a victim in any danger. The person engaged in the chat was a member of law enforcement.”

She said that Schmidt had pleaded guilty because he wanted to be held accountable for the crimes he had committed, and because the district attorney’s office was ready to go to trial.

Schmidt had been arrested on Dec. 2, 2017, along with three other men, in a sting conducted by the Albany County Sheriff’s Office, spokesman Chief Deputy William M. Rice told The Enterprise earlier.

Also arrested in the operation spearheaded by the sheriff’s office with help from the New York State Police Computer Crimes Union, Colonie Police, and the Federal Bureau of Investigation, were Daniel P. Meyer, 20, of Baldwin in Nassau County; Edward T. Neville of Pennsylvania; and Russell D. Blair of West Sand Lake.

Rice told The Enterprise at the time of the arrest that language had been placed into social-media posts that would serve as a signal to people looking to have sex with children. The men were first given the location of a hotel and then, when they showed up, they called or texted someone and were given the room number.

Rice said at the time, “We give them multiple opportunities to not go through with it … to change their mind and walk away, but they don’t — they can’t.”

Carter set his sentencing for Dec. 5 and released Schmidt on his own recognizance.