Bigfoot and Pacifist mode

Saw something yesterday, which reminded me of something I'd often see at the end of Radiation Rumble. Bigfoot arrives after the event is over, so pvp is turned back on. And as it was, people were going berserk and shooting like crazy. Other players were running around and so running in front of other players and getting shot. I kept getting the message "You're in pacifist mode and cannot do damage" (or whatever it actually says).

But as soon as Bigfoot went down, I then saw players, (strangely lower levels attacking higher levels), turning on each other. This is not on guys! The only solution I can think of (besides everyone having pacifist on) is containing the Bigfoot appearance to inside the event. Anyone else see this behaviour?