Every paintball player who has ever heard of the pepper ball launcher knew it was a disaster waiting to happen. Still not sure how she died exactly, but a normal paintball in an unprotected eye is usually the end of the eye. The FN303 rounds are full of bismuth and weigh a lot more than a normal paintball, but go at similar speeds, so there's a lot more kinetic energy involved. Additionally, paintball guns are generally tested before and after games to ensure that they are in the safe velocity range (under 300 FPS) but the mechanisms are capable of producing much higher velocities if out of tune. The highest I've ever seen on a chronograph was 425 FPS. I've also seen a paintball-specific goggle lens cracked in half by an out of tune paintball gun.
From FN's site:
Warning: For safety reasons never aim toward face, neck or throat. Only factory authorized projectiles are to be used in the FN 303 Launcher. Do not use the launcher or projectiles before carefully reading the operators manual. Authorized training is available through FNH USA and highly recommended before deployment of the FN 303.