How do I make a fire trigger for zombies and players?

Game Modding | Call of Duty: Black Ops 3 | Radiant

Vitzeee:

I swore I seen a video on the zombies and fire effect on your screen but I can only find this one now.
Pretty much like the video but from town where zombies will walk over the lava and catch fire same as you, Ive looked and looked but cant seem to find the video i saw before.