Derek Sanders, the elected sheriff of Thurston County, said in a Facebook post that the U.S. Army Criminal Investigation Division asked his office for assistance Monday as an FBI special weapons and tactics team executed a search warrant in Lacey, near the state capitol of Olympia, “as a result of a violent robbery and theft of military weaponry/armor.”

The U.S. Attorney’s Office in Seattle said in a statement to The Associated Press on Tuesday night that the search warrant related to an Army CID and FBI investigation into an assault Sunday at Joint Base Lewis-McCord, just north of Olympia.

Sanders’ statement said two people were arrested and booked into Thurston County Jail for investigation of firearms-related offenses.