The bombs used by the pair varied and were crudely made from carbon dioxide canisters, galvanized pipe, and metal propane bottles. The bombs were primed with matches placed at one end. Both had striker tips on their sleeves. When they rubbed against the bomb, the match head would light the fuse. The weekend before the shootings, Harris and Klebold had purchased propane tanks and other supplies from a hardware store for a few hundred dollars. Several residents of the area claimed to have heard glass breaking and buzzing sounds from the Harris family's garage, which later was concluded to indicate they were constructing pipe bombs.