How to use
Pressing Z will open the Guard Commands menu, letting you select wich squad you want to handle.
Commands
Press ALT to enter commands mode. Instead of shooting, you will issue commands until you exit the mode pressing ALT again.
The commands you can issue depend on the Squad Leader's situation. Here's a list of currently supported commands and situations:
Squad is on foot
Aim+click at ground = Run there
Aim+click at a ped = Attack him
Aim+click at a vehicle = Enter that vehicle