How do you miss with a scoped rifle while prone at that distance? Unless it is horribly sighted or you are unstable, should hit fairly close to the cross hair. May hit a bit higher if it is sighted for long distance, but I'm assuming he was aiming towards the center (head or chest) and not the leg hitting the shoulder (shouldn't be that much of a difference this close if set for a farther range.)
Rocket launcher should be the best weapon, but his power is airsoft gun so I guess his weapons are limited to guns, and not explosive weapons like grenade and rocket