By Kevin Liffey (Reuters) - U.S. police are under pressure not only for the killing of an unarmed teenager in Ferguson, Missouri, for which a grand jury decided on Monday not to indict the police officer, but also for the military-style response to the sometimes violent protests that followed. The sight in August of police in camouflage gear, backed up by armored vehicles and brandishing assault rifles, was a reminder that some U.S. police departments have recently acquired U.S. military-surplus hardware from wars abroad. ...