Story highlights Charges are expected against Airman 1st Class Nico Cruz Santos

Santos is awaiting sentencing on unrelated charges, officials say

The Air Force member had a gun and cell phone, and had been talking with authorities

The Colorado Springs air base is home to the 50th Space Wing

An armed airman who allegedly barricaded himself inside a building on a Colorado air base is awaiting sentencing on unrelated charges and will likely face additional charges, the base said Tuesday.

Airman 1st Class Nico Cruz Santos, 21, surrendered to authorities late Monday night after an hours-long standoff with authorities at Schriever Air Force Base. No one was injured.

"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 Ross, 50th Space Wing commander, in a Tuesday statement. "Our law enforcement and community partners worked together to ensure the security of our mission and people while helping this airman through a troubling situation."

The airman -- who belongs to the base's 50th Security Forces Squadron -- locked himself around 10 a.m. inside a building where personnel get paperwork and equipment before being deployed, said Lt. Marie Denson, a spokeswoman at the Colorado Springs base.

Soon thereafter, that building and the surrounding area was evacuated. Law enforcement units and other first responders from the Schriever base, nearby Peterson Air Force Base and the El Paso County, Colorado, Sheriff's Office SWAT team rushed to the scene, Lt. Col. Harold Hoang said.

The man was armed with a personal handgun, authorities said.

He also had his cell phone, which he had been using -- along with a land-line phone -- to communicate with military officials outside. Mental health professionals were also on site, Denson said.

The airman "is currently facing legal action in a civilian court as well as disciplinary action and possible discharge from the Air Force," Hoang said.

The base said in a statement Tuesday that Santos is awaiting sentencing in Gilpin County on unrelated charges earlier this year.

"It is expected that once the investigation of yesterday's incident is complete that additional charges may be filed in either the military or civilian court systems," the statement said. The incident remained under investigation Tuesday.

Santos was being held in a Teller County detention facility, the base said.

Schriever Air Force Base is also home to the Space Innovation and Development Center, the Missile Defense Agency, 310th Space Wing and other units and groups, according to its website.