I was playing then POUFF! it crashed

I was playing In multiplayer then it crashed,We were spawing massive big of mobs 30+ then It just crashed.

Steps to Reproduce:
1. Enter a multiplayer server
2. Go in creative (have to be an admin/OP)
3. Spawn 30+mobs including creepers,zombies and skelletons
4. Profit?

I really don't know what happend it just crashed....
Like a famous Character once said : I JUST DON'T KNOW WHAT WENT WRONG! D: -Derpy Whooves