I think this is basic memory hacking, if you freeze the ammo of your weapon (lets say the weapon got 20 bullets) the weapon will continue shooting after you are out of ammo, but the difference is, all bullets after the last one (21) will cause no damage, so it looks like you have unlim. amo and your enemy (in this case his friend) is invunerable
so this two mofos could be some newbs who have found out the magic of a memory searcher or real hackers with the same effect like the memory hacking, but I think it's the first case