Just to be safe, try to remember the names on your friendslist, and only use weak lvl 1 attacks against bosses spawned by those people. Well, except maybe when their boss is about to expire.
If they wanted the boss to get killed as fast as possible to make place for another, they should've released it to nuka town instead of allies only.

The special 100 million HP event bosses rarely happen. In case they do have one sometime, I'm sure it'll be all over these forums to keep an eye out for those.