1) Add the following to your init.sqs
unitsArray = [chaseunit1, chaseunit2, chaseunit3,....]
where chaseunitX are the names you have given to whatever units are chasing your player. If you have placed a crewed vehicle in the editor also add it to this array.
2) Add a trigger with the following Condition
({(huntedunit distance _x) <= 1} Count unitsArray) > 0)
Where huntedunit is the name of your player unit. If this is a single player mission you could substitute player for the player unit's name.
If you have many units chasing the player and they start in a separate area you could instead put a trigger that covers all the chasing units(but not the player unit), set it to fire side present once with the On Activation
unitsArray = +thislist
Then you neither need to name all the chasing units nor use the line I have given for the init.sqs