I shot a gun in my backyard on accident; my uncle in law was a cop, and he kind of forgot to keep the handgun on safety as he handed my nine year old self the firearm to hold... and my finger kind of slipped-

ALSO
I FORGOT TO MENTION
When Boxes and Flames come into play, the latter will probably arrive sooner (though I wouldn't say that they'll be there for the next arc, not sure) while Boxes won't be touched upon until the late third arc or the Future. But when it does happen, there's something I want to emphasize:

[b]One character, one Flame, one Box.[/b]

Unless they're really, really special. Like Sonya and Vector, as of now.
The reason is, is that even having one Flame itself is exceedingly rare. Two Flames is just outright unheard of. And even if one possessed multiple Flames, it'd take a very very long time to even use one with some capability-