President William McKinley was killed by two rounds fired from a .32-caliber revolver. This revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing, with the modern revolver being invented by Samuel Colt. As the user cocks the hammer, the cylinder revolves to align the next chamber and round with the hammer and barrel, which gives this type of firearm its name. The hammer-cocking happens either directly (via the shooter pulling it back) or indirectly (via the first portion of the trigger pull in double-action revolvers.) In modern revolvers, the revolving cylinder typically chambers five or six rounds, but some models hold 10 rounds or more. Revolvers are most often handguns, but other weapons may also have the design of a revolver. These include some models of grenade launchers, shotguns, and some rifles.