The best way to do it is to keep on restarting until you start near the tommy gun x2 and then collect it and wait at the end of the passage and shoot the handymen when they come. Reload by pressing triangle when they have gone and see if the tommy gun has reapearred. Keep on repeating this. I managed to get the gold with only 0.3 seconds remaining. How lucky was that!!!

you go to the toll booth looking thing and get the double tommy guns. Then, right where u got the guns you crouch and wait for the handymen to come. when they come move forward and it will raise your crouch just enough to shoot them but remain unharmed from them. u can get a platinum this way!