in the trigger you want to start the salute type []exec"salute.sqs"
then make a text file in the mission folder and name it salute.sqs (make sure you allow view of file extensions in your folder options). Inside the script type the following:
unit1 fire"m16"
unit2 fire"m16"
unit3 fire"m16"
add a line for each unit you want to fire, and remember to name them in the editor
Also, if you want it to happen slow then type setacctime 0.3 at the beginning of the script and then setacctime 1 at the end of the script.