The Nebraska man charged with shooting up a Sonic drive-thru, killing two employees, is now accused of stabbing an inmate in lockup. “He shanked me with something sharp and flushed it down the toilet,” victim Derick Fuller told investigators after the May 12 attack at the Sarpy County Jail, according to KETV. Authorities said when they found Fuller bleeding on the floor of his cell, Roberto Silva Jr. was just standing there and refused to answer any questions. Silva, 23, was first arrested in November for ordering $57 worth of food from Sonic on someone else’s app. He allegedly then returned days later in a U-Haul filled with guns and incendiary devices and opened fire.