Distance tag dosen't work when executing /kill

When I executed the command /kill @e[type=zombie,distance=3] about 1 block away from a nearby zombie, it said entity not found.
For some reason I can't upload screenshots because I am missing a token or something.
So here are some links:

https://imgur.com/a/QWnOw

One of the photos shows me writing the command and the other one is the command not working correctly I think.