A former aide to Sen. Maria Cantwell (D-Wash.) pleaded guilty on Thursday to one count of possession of child pornography, U.S. Attorney Jeffrey Taylor announced.

James McHaney entered the guilty plea before Chief Judge Thomas Hogan in the U.S. District Court for the District of Columbia. McHaney, 28, faces up to 10 years in prison and a fine of $250,000.

A sentencing date has not yet been set. An attorney for McHaney could not immediately be reached for comment.

The government’s case centered on a cooperating witness who was working undercover for law enforcement.

The witness — who had met McHaney before and exchanged images of child pornography with him — made contact with McHaney online at about 12:15 p.m. on Nov. 30, according to a press release issued by the U.S. attorney.

After about 10 minutes of chatting using an instant messenger program, the witness asked McHaney about his work schedule that day, with McHaney responding that he could take a long lunch, the release said. The witness then asked McHaney if he wanted to have sex with a 13-year-old boy, and McHaney replied: “I’ll be there.”

Plans then were made for McHaney to meet the witness and the boy at the witness’s residence, according to the release. McHaney asked the witness what the boy looked like, including questions about whether the boy had pubic hair.

The witness replied “barely any pubes” and “none under his arms,” with McHaney answering: “hot,” the release said.

McHaney also agreed to bring videos and a flash drive with hundreds of images of child pornography to be used as “visual aids,” according to the U.S. attorney.

At about 1:15 p.m., law enforcement officers saw McHaney in the lobby of the witness’s residence, located on the 1300 block of U Street Northwest. Officers immediately placed him under arrest.

Investigators also discovered more than 600 images of child pornography on the flash drive, the majority of prepubescent males.

According to the U.S. attorney, McHaney “possessed these images for his personal use, and to distribute them to others.” Several movie files depicting scenes of child pornography also were discovered on the flash drive.

The Metropolitan Police Department and FBI worked cooperatively on the case, the release noted.

Cantwell fired McHaney almost immediately after his arrest, pledging to cooperate with authorities.