f8 mode when /kill

i was adventuring in the new snapshot, and i wanted to go back to the spawn, and i did /kill. And when i spawned again, i thougt, did i hit f8? But no, i thought that i hit a button so i quit minecraft, and open it back up, and it was fine again. Then i had to kill myself again using the command, and i found out that it was a bug, so when you do /kill, you get in f8 mode, and cant get out without quiting minecraft.