While playing the game, i was mob grinding for xp, and i went to my mines which is about 15-25 blocks away from the mob spawner and there was a zombie at my mine entrance door. I was going to open it and kill it but when i got to the door it hit from the door. I even went to my creative world and tested it out on all the doors including doubled and single doors.

Steps for this to happen
1: Have a zombie behind a closed door.
2: attack or kill another zombie out from the door.
3: Go to the door.
4: Bam! get attacked by the zombie.