What happens next?

How to prevent crimson heads in resident evil
Decapitate it.
Shotgun: to blow off its head, wait until the zombie gets really close to you, and then aim up and fire. Handgun/samurai edge: after two well placed shots to its upper chest, you might get lucky and blow off its head on the third shot.
Also, when you and the zombie are at slightly different elevations and you aim up or down to its level, you have a higher chance of scoring a headshot. Samurai edge gets more headshots than the handgun.