When the /kill command is applied to all entities, Wither Skulls that are being shot get stuck mid-air with no properties.
What I expected to happen was that the Wither Skulls would disappear when "killed", as the command would suggest, and they would disappear without trace.
What actually happened was that the Wither Skull was visually stuck in mid-air, and all of its properties were removed, meaning you could go through it without it exploding.
Steps to Reproduce:
1. Spawn a Wither. Have some other mobs around as well so that it will start firing Wither Skulls.
2. While the Wither Skulls are in mid-air, use the /kill @e command.
3. If you go back to the area the Wither Skulls were in, you should notice they are seemingly stuck in the air, with no properties.