spexel: this is not relevant to this topic.
dd a condition to your event 10
System: compare two values
Compare Shotgun.count = 0
For this to work you also need to add a shotgun.destroy in start of layout (event 9)
Also in your event 10 you use a random function.
This means that every tick, this value gets changed. You probably should rather use a global variable, and assign it in the action of event 10, not in the conditions of event 10
(each time event 10 gets executed, you set the next random time a shotgun will spawn).