Killing Mobs With Explosive Fireworks Shot From Crossbow Doesn't Count As Player Kill

When loading a firework crossbow then killing any mob with it, the mob doesn't drop any xp.

Steps to Reproduce:

1. Load a crossbow with explosive fireworks
2. Kill any mob that should drop xp when killed by the player

Observed Results:
The mob didn't drop any xp.

Expected Results:
The mob would drop xp.