When Dr. Hawkins is telling you how to fire your weapon, move, etc. get to
the point where he says he placed a grenade somewhere around there. Then
go pick up the grenade but do not throw it. Go to sniper mode and hit the
ball in the doorway that keeps you from getting through it. This will
cause Dr. Hawkins to stop talking and will take away the grenade from your
inventory but it will make Kurt invincible! Well worth it!