Fellas, how can i add fire?

[Timohaer ua]

How can i add the thing to my map, that will set on fire in exact hitbox with fire effects and instantly burn to death every player inside it. This would happen once per 5 or 10 seconds. And if you are curious, this will be a rocket, and i would also appreciate if you help me add a suitable for rocket sounds (Probably a pyro`s stock flamethrower, but i dunno how to)

This might be possible, i guess