New details about the background of an Immigration and Customs Enforcement officer accused of fatally shooting a Colombian man in Maine have raised fresh questions about the agency’s hiring and training practices. David Brouillette, an ICE officer from Gardiner, Maine, is accused of shooting 25-year-old Johan Sebastián Durán Guerrero during an immigration operation in Biddeford on July 13. Guerrero was inside a car when at least four bullets passed through its windshield. He died at the scene.…