Goofs

Alex uses a suppressor (silencer) on her high-powered sniper rifle. The main reason modern snipers commonly use suppressors is not to silence the shots, which is not very effective on a high-powered rifle (they will still be quite loud, which is correctly depicted in the film); the main reason is to eliminate muzzle flash, allowing the sniper to make follow-up shots without revealing her position. Despite this, the rifle produces plenty of brilliant orange muzzle flash during the church tower scene.

Alex and Carole, who are expert career criminals, seem blithely unconcerned about getting caught. They leave behind an ATV, guns, picnic supplies, and various other gear they've been handling barehanded. Carole evidently planted the picnic basket with a 9mm handgun in it, an obvious sign that the basket's owner is up to no good, inviting a stakeout should police find it. Alex stands up in the prominent church steeple wearing a brightly colored tracksuit after gunning down several bad guys in broad daylight; it was established that it took her several minutes to climb up to her position, so police or other bad guys would have a similar amount of time to arrive before she climbs back down.