Officials at the 50th Space Wing at Schriever Air Force Base have identified the 21-year-old airman who barricaded himself at the base for hours on Monday.

Airman 1st Class Nico Cruz Santos peacefully surrendered after a day-long standoff. He had armed himself with a handgun and locked himself in a room at the base.

The standoff, which ended about 8 p.m. Monday night, put the base on heightened security. Outside law enforcement agencies were on scene to assist Schriever security.

According to base officials, Santos is with the 50th Security Forces Squadron and faces possible discharge from the Air Force.

Officials say he entered the Deployment Processing Building on the base’s west side about 10 a.m. with a personal handgun. The building was evacuated. Santos did not take any hostages.

He was in contact with negotiators throughout the day on his phone and surrendered peacefully. Base officials said he was in the custody of local law enforcement Monday night, but he may be transferred if military courts get jurisdiction of the case.

Santos has been on active duty with the Air Force for nearly three years but was facing disciplinary action and possible discharge from a legal action in a civil court, said Lt. Marie Denson, a base spokeswoman. She did not release details on the legal action.

Security officials continue to investigate the case, including how Santos brought a gun onto one of the nation’s most secure bases.

The base, which is home to the 50th Space Wing and about 10 miles east of Colorado Springs, controls the nation’s military GPS satellites. Operations at the base were not disrupted, Denson said.

She said the building in which Santos barricaded himself is used by those planning a deployment and is not essential to the work of the rest of the base.

“Everywhere else on the base it was business as usual,” she said.

No shots were fired and no one was injured in the incident.

“We are grateful for all our first responders in their professionalism that was critical to the peaceful resolution of this situation,” said Col. James P. Ross, 50th Space Wing commander, in a statement.