nothing special
I don't think you're quite understanding, there's a new plugin on the server that allows you to hit projectiles back with your melee weapon. The Ball is one of the only confirmed projectiles that cannot be reflected back. It stops in mid-air and just falls.
The story is that Didier was going in for a backstab on hale while he was moving, at the same time a scout hit a ball to stun hale as hale was swinging. Hale reflected the ball. Basically, Didier got killed by a non-moving projectile.