86
The intended target was Louis Phillipe of France. It fired once. Out of 25 barrels four misfired, four barrels exploded, and the would be assassin forgot to load one, and it still fired enough projectiles to kill 18 people, wound 18 people, wound 4 people more so badly they lost limbs, and also hurt the assailant himself from the exploding barrels. The king got a light scratch.
The builder of this infernal machine, Giuseppe Marco Fieschi, was given an honorary funeral service by the Reactive Scientific Research Institute, the developers of the Katyusha rocket system, a century after his death.
I can tell you why one of them probably misfired, you got a bent barrel right there in the middle.