I got "Heads up!" the other night. I threw down a care package and sentry gun marker in the corner on Rust. Killed two guys trying to steal the care package, then turned around to cover my ass. Then I hear that CSI-Miami YEEEEEEAAAAAAAH sound and get a CHALLENGE COMPLETED - HEADS UP notice. The Sentry package came out of the sky and domed this guy who was trying to steal the care package I guess. I never thought I'd actually get that challenge.