On the afternoon of May 17, 1974, elements of a group which called itself the Symbionese Liberation Army (SLA), a group of heavily-armed leftists, barricaded themselves in a residence on East 54th Street at Compton Avenue in Los Angeles. Coverage of the siege was broadcast to millions via television and radio and featured in the world press for days after. Negotiations were opened with the barricaded suspects on numerous occasions, both prior to and after the introduction of tear gas. Police units did not fire until the SLA had fired several volleys of semi-automatic and fully automatic gunfire at them. In spite of the 3,772 rounds fired by the SLA, no uninvolved citizens or police officers sustained injury from gunfire.
By the time of the SLA shoot-out, SWAT teams had reorganized into six 10-man teams, each team consisting of two five-man units, called elements. An element consisted of an element leader, two assaulters, a scout, and a rear-guard. The normal complement of weapons was a sniper rifle (apparently a .243-caliber bolt-action, judging from the ordnance expended by officers at the shootout), two .223-caliber semi-automatic rifles, and two shotguns. SWAT officers also carried their service revolvers in shoulder holsters. The normal gear issued them included a first aid kit, gloves, and a gas mask. In fact it was a change just to have police armed with semi-automatic rifles, at a time when officers were usually issued six-shot revolvers and shotguns. The encounter with the heavily-armed Symbionese Liberation Army, however, sparked a trend towards SWAT teams being issued body armor and fully automatic weapons of various types.