A 10-year-old girl was killed as she rode her bike near her Moreno Valley home by a bullet that discharged accidentally from a high-powered rifle that two men had been examining in a garage, authorities said. The two men, Daniel E. Cunningham, 45, who lives on the street where Monique Marie Merendon was shot, and Jon M. Higbie, 52, of Riverside, were arrested for investigation of allegations that they had failed to take safety precautions in handling the rifle, which Riverside County sheriff's deputies said had been modified by Cunningham. The rifle fired as Cunningham handed the weapon to Higbie. The bullet struck the girl, who was riding across the street, Higgins said. The two men were released on bail.