Stone said that police officers were searching the bodies of the gunmen. They feared they had used their pipe bombs to booby-trap corpses, including their own. At 4:30 p.m., the school was declared safe. At 5:30, additional officers were called in, as more explosives were found in the parking lot and on the roof. By 6:15, officials had found a bomb in Klebold's car in the parking lot, set to detonate the gas tank. Stone then marked the entire school as a crime scene.