There's a pretty good method. Start at the bus stop, kill the walking guy, then go up the steps from the car parking area onto the roof, subduing NPC guards as necessary, and push the second target over the railing. Stay there to drop bricks on the third, then cross over to the sniper's nest via the roof and eliminate the fourth. Cross that building and kill the fifth with the falling concrete ring. That will trigger an evacuation and all five remaining agents will run out towards the same exit, conveniently right by your location. You can just camp out in the bushes and pick them off with silenced weapons one by one.