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.

ICE filed an active immigration detainer on Granados-Alvarado, a citizen of El Salvador, with the Montgomery County Department of Corrections and Rehabilitation the following day. When Granados-Alvarado posted a$2,000 bond, Montgomery County officials let him out of jail instead of holding him for ICE agents. (RELATED: ICE Files Detainer Against El Salvadorian Student Who Brought Stolen AR-15 To Maryland High School)

In its statement, ICE confirmed that Montgomery County is a jurisdiction that “has publicly limited cooperation cooperation with ICE” and “frequently ignores legally authorized detainers.” (RELATED: Rockville High Protesters Rip State, County Governments Over Sanctuary Policies)

The U.S. Border Patrol first detained Granados-Alvarado on March 6, 2014 about 80 miles southwest of Corpus Christi, Tex., reports WJLA7. ICE says the teen was previously issued a notice to appear in immigration court and has “multiple criminal arrests” on file.

Granados-Alvarado is currently detained at the Howard County Detention Center in Jessup, Maryland and is going through removal proceedings, immigration officials said Monday.

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