I got this trophy while defending on Dorado by going to the top of one of the tall buildings with a balcony about half way through the map (after the first checkpoint). That stretch usually has the most of the attacking team trying to escort the vehicle through and they are not typically looking up high. When they hear "It's High Noon" they will start to scatter. I got it mid-air while jumping off the balcony down to the ground to get everyone.