EL PASO COUNTY, Colo. -

Officials say a man who is accused of taking a handgun onto Schriever Air Force Base and barricading himself in a building is awaiting sentencing on a charge of attempted sexual exploitation of a child.

Officials have identified the man as 21-year-old Airman 1st Class Nico Cruz Santos.

Santos surrendered peacefully around 8 p.m. Monday. The standoff began around 10 a.m., officials said, when Santos barricaded himself in an office at building 780, the base deployment building. He is a member of the 50th Security Forces Squadron at the base and has been in the Air Force more than two years, officials said.

Santos was armed with a personal handgun, said unit commander Lt. Col. Jasin Cooley, and described him as "suicidal, but not homicidal."

"One of the members stayed on the phone with him for much of the day," said Cooley. "We were able to convince him that (surrender) was the right thing to do."

Prosecutors say Santos pleaded guilty in September to attempted exploitation in Gilpin County west of Denver. He faces up to 18 months in prison. Sentencing is Dec. 16.

It is expected that once the investigation of Monday's incident is complete that additional charges may be filed in either the military or civilian court systems. According to Cooley, Santos will be charged with brandishing a firearm and bringing a firearm onto the base. Cooley also said because Santos did not live on base, he was not subject to a thorough search and also failed to declare that he had a personal handgun.

Santos will be held in the Teller County Jail because the base doesn't have a jail. The base and jail made a previous arrangement, Cooley said, for just such occasions.

Officials evacuated building 780 during the incident. Responders included base security forces, deputies and a negotiator with the El Paso County Sheriff's Office, and security personnel from nearby Peterson Air Force Base.

"While there are lessons to be learned from every situation, by and large yesterday's incident was resolved with the best possible outcome," said Col. James P. Ross, 50th Space Wing commander.

The standoff caused only minimal disruption to base operations, officials said.