At 6 p.m. Tuesday, Chelius, working undercover, met with Cook and Roberts to buy mescaline while four other undercover agents watched, other officers said. Cook and Roberts tried to run away but were arrested by the other agents who had observed the drug sale in a field next to a supermarket in Sacramento's north area, sheriff's spokesman Bill Miller said. Miller said the youths were sitting in a pickup truck when Chelius approached them. After he bought a large quantity of the hallucinogenic drug, Chelius identified himself as a police officer and told the youths they were under arrest, Miller said. One of the youths drew a two-shot pistol and shot Chelius, who fell to the ground. The youths jumped from the truck and ran toward the back fences of nearby homes, but were caught by the other agents, Miller said. Chelius joined the state agency December 1, 1973, after working for the Carson City Sheriff's Department. He was a senior agent described by Calhoun as a working supervisor. Nevada Governor Robert List, upon hearing of Chelius' death, called Chelius' widow Ilse, to console her. Chelius also is survived by three children, Toni 13, Shawn 11, and Jason 8.