Fireteam bug

So either the FT lag switching or I just had the worst bug ever. I was doing great keeping distance still had my second wind and a little over half health. BOOOM insta killed. How did it happen i have no clue just alive and fine to dead no second wind no starting self destruct just dead. I thank it has something to do with the hammerhead or the other grenade launching gun. Oo and the reason i thank it was lag switching one of them was running into a wall right before I died.