SAN DIEGO — Prosecutors have charged a 23-year-old former San Diego County sheriff’s deputy with second-degree murder for fatally shooting an escaped inmate outside the downtown jail in May.

Aaron Russell is scheduled to be arraigned Tuesday in connection with the shooting death of 36-year-old Nicholas Bils. Russell faces 15 years to life in state prison if convicted. He remained in custody with bail set at $1 million.

Bils who had been arrested by rangers with the California Department of Parks and Recreation for allegedly threatening a ranger with a golf club at Old Town San Diego State Park, was being transported to the downtown detention facility when he managed to escape , police said.

As Bills ran off, Russell, who was walking to work with another deputy, saw him. The two deputies ran after Bills, and moments later, Russell shot the fleeing man and fatally wounded him.

Exactly what prompted the deputy to open fire remains unclear. The DA’s Office said there is surveillance footage of the shooting, but it will not be released to the public at this time as it is now evidence in a pending criminal case.

District Attorney Summer Stephan said, “We reached the decision to file criminal charges following a thorough review of all the objective facts and evidence in this case by specialized prosecutors and investigators in our Special Operations Division. When a life is taken, we must make decisions based in facts and law, and not ones that are influenced by the status of the accused as a peace officer nor the status of the victim. These decisions must be made solely in the interest of justice and not based on favoritism nor public opinion.  Every person must be accountable under the law.”

Russell had been with the department for 18 months at the time of the shooting, according to the San Diego Police Department.