Once helicopter is destroyed, it goes into "destroyed" state and then keeps flying barely above ground and keeps shooting without being able to be destroyed. I don't have any plugins related to events or helicopter.

Plugins:

AntiWounded
BetterChat
BetterChatMentions
DeathNotes
DropRemover
GatherManager
InstantCraft
Kits
Metabolism
Nobackpacks
NoLoot
NoRespawnCooldowns
StatTrack
TemporaryBarricades