A person died wrongfully
"I didn't mean to" = involuntary manslaughter at a minimum
that's why it is called "involuntary" if there is no intent and the consequences of incarceration of such crime should be implemented accordingly. With the degree of negligence and willful disreguard for safety with a deadly weapon, it could be argued as more than involuntary manslaughter. The owner of the weapon could (or arguably should) also face similar charges.