Federal immigration officials excoriated the Montgomery County, Maryland government on Monday after jailers knowingly released an 18-year-old illegal immigrant who allegedly brought a stolen AR-15 rifle onto school property.

U.S. Immigration and Customs Enforcement said the county released Mario Granados-Alvarado on May 3, despite a formal detention request lodged with jail officials the previous day. ICE was able to locate and arrest Granados-Alvarado On May 4, but the agency called out Montgomery County for refusing to keep him in detention until immigration agents could arrive.

“Keeping people safe means not tolerating the release of aliens that present a clear public safety threat back into our communities,” Dorothy Herrera-Niles, field office director for Enforcement and Removal Operations (ERO) Baltimore, said in a statement. “ICE is committed to fostering positive collaboration with our local law-enforcement partners, and welcomes changes from county officials that would prioritize public safety.”

Police arrested Granados-Alvarado on May 1 after a school resources officer at Albert Einstein High School questioned the teen about his involvement in the theft of an AR-15 from the trunk of a Rockville Police Department cruiser, WJLA7 reported. Officers subsequently found the rifle in the trunk of Granados-Alvarado’s car, which was parked at the school.