A dog walker called 911 to report the incident before it became apparent that the unmarked vehicle belonged to federal law enforcement, when men in U.S. Despite multiple inquiries, States Newsroom was not able to get any additional information on the man taken into custody. HSI is a law enforcement agency within U.S. Immigrations and Customs Enforcement, under the Department of Homeland Security. District Mayor Muriel Bowser, however, has agreed to keep federal law enforcement on the streets beyond Trump’s emergency, which ends Wednesday. States Newsroom contacted the mutual aid organization but could not obtain any details about the Sept. 3 incident.