If you have a world and spawn a Zombie via

/summon Zombie ~ ~1 ~ {Equipment:[{},{},{},{},{Damage:3,id:397,tag:{SkullOwner:}}]}

and you hit him, you screen turns red and upside-down chests appear. But if you kill this Zombie and hit another Zombie once, everything turns back normal. I'm sorry but i have no idea of what's happening there!
EDIT1: Also, if you hit the weird Zombie and go to the minecraft startup screen, everything is pixelated instead of blurred!