Being hit by zombies...but there are no zombies in room!

[fioio 1]

So I was being followed by 4 very fast zombies...I entered a house and knowing that they cannot climb stairs, I went to the upper floors. To my amazement, these zombies were nowhere to be seen, but still hit me. In fact, the screen was greying out as if being hit, and I became unconscious almost immediately.

 

Anyone else noted this?

[Xenithon 28]

They're hitting you from beneath the floor, you're only safe if you're on either a high-up 2nd floor or a 3rd floor.

[smrtrthanavgbear 11]

I know what you mean, but in my case, zombies will punch me, at full speed, always in range to hit me, if i stop,  they seem to start lunging at some object several feet away, but my screen grays just the same.