Insta killed

I’m not sure what happened and I couldn’t get a replay of it but I was fighting a team on Dire Marsh when me and my team got ambushed by another team and it was so instant I don’t know what happened but from full health I got insta downed, so quick that my friend couldn’t react in time and when he saw that I was down he got insta downed as well, my other teammate that was a random managed to survive but then died later, I’m just looking if I can get a replay of the situation to know what killed me and whether it was a bug of sorts or just a really good synergy with some weapon and equipment. Thanks!