Thunder rain effect sound

I want to make that, every random certain time (see example 1), a thunder sound file plays, but, that the engine chooses a random sound from a list (example 2). I know it sound hard but how do I make this?.

ex 1:
Selects random number from 50-75, then that’s the seconds.
so2.wav < Randomly picks this one, then plays it at the righ time

Maybe with variables? Begin a timer, and then have a condition that when the timer reaches a RandomInRange between 50-70, that it sets a scene variable to RandomInRange between 1-4 (and also restarts the timer). Then have four events that are “If variable Thunder = 1, then play sound so1.wav (trigger once)” and so on for all four sounds.