If a kickoff is fumbled into the end zone can it be downed?

If the player does not step outside of the end zone before stepping out, then it is ruled a touch-back and the ball is placed at the 20 yard line.

However if he steps out of the end zone then steps out inside the end zone it is ruled a safety and the other team gets 2 points and the team that stepped out in the end zone then gets a free punt.