There is one picture there-- if you look at the one where Boris the Flesh Construct is facing off against all the zombies on the road you can JUST see one of their finned helmets beyond the pack 'o' undead. Both of the Rocket Troopers did rather well, in fact. They didn't actually take out any zombies, but they kept bullet striking the pack and knocking them back a bit each time. Between that and the shooting of the GIs the zombies had a hard time getting to the bridge.
Since shooting could do virtually nothing to the zombies unless you rolled a one for a head shot, Marc had each hit knock the undead bastid back a half inch. It made the US player feel that it was at least somewhat worthwhile to try even if the odds were slim to "kill" one.