|The following is based on Van Buren and has not been confirmed by canon sources.|
Kill or drive off the Jackals. You'll really need to kill them, since they tend to run away already. Note they also have a blockade between Denver and Boulder that you need to destroy for this to count. If ZAX fails and the doors open, the Jackals (if still alive) will invade. You can create quite a death toll that way.