I'm pretty sure they made the vocals themselves. By that, I mean they cut the original vocals into parts, then changed their pitch and put everything into the drop. The drop sounds pretty simple though. Looks like a kick, a bass (made up of filtered sawtooth wave) and the vocal part itself.
Also, if you're not sure how to exactly make such vocals here's a video for you:
YouTube
In case you don't want to make them yourself, you can always download pre-made ones from splice.com, although it requires you to buy the membership (which is only 8$ or so a month)
Anyways, good luck producing!