Look at the kill message feed in the top left, where it usually says "Player1 > [icon] > Player5" or something. How does it say you died? Does it have a car icon, falling icon, skull icon, or something?
Could be a glitch death, suicide death, or death by falling...if you don't have Maneuverability and fall without Armor on, I think a ~20m drop can kill you. It's pretty funny. But it should still say how you died in the kill feed.