How would you set up a projectile that isnt being fired from a gun/person?

We are creating a VR project and in one of the sequences, we are destroying quite a large structure. We want it to be destroyed by incoming projectiles that are triggered with box triggers when the watcher enters a certain area.
The only control the viewer will have will be their head movement.

We have only found ways to destroy buildings when the viewer shoots the walls.

Any suggestions?

I would use a trigger volume to tell the server to spawn a projectile and fire it at the structure. Since your server is probably a listener server (the player is the host) then you’d kind of in a sense be having the player spawn the projectile, although they wouldn’t be doing it with user input. It would just be a triggered event.