Story Link RENO, Nevada (CNN) -- Accused mailbox bomber Lucas Helder told authorities he was planting pipe bombs in a pattern to show a happy face during his five-state weekend cross-country spree. Helder made the admission to an undercover officer present at his arrest, according to Lt. Thom Bjerke of the Pershing County, Nevada, Sheriff's Department. "He seemed kind of carefree or amused about what was going on, " Bjerke told CNN's Paula Zahn. Helder has admitted he planted 18 pipe bombs in five states, knowing that people would be injured when they exploded, assistant U.S. Attorney Craig Denney said Wednesday. Helder will be moved from Reno, Nevada, on Friday, according to Assistant U.S. Attorney Rich Murphy in Cedar Rapids, Iowa.