100dmg no kill ?

wierd. I joined the new escape map had 60 fps + 60 ping all was normal , no lag but then wanted to kill a guy but didnt kill and I lol'd hard .
Pic:

I did 100dmg but didnt kill him ? he had normal ping too around 70 .
But one guy was saying ''Stop hack , Stop hack '' maybe he hacks ? well asfar i saw him he didnt have any visible hacks. So is this a hack or bug or lag or idk what

This isnt photoshopped. Well as you can see idk how to make straight lines in gimp . -.- i lost my paint or deleted it idk.

i think he had unlimited health hack../