"In Alien vs Predator - Requiem The Scatter gun is part of the Plasma Caster it is a last resort hand-held plasma gun that fires a net of energy out to a long range. The weapon is, unfortunately, very clumsy, taking up a hand which can be replaced by melee weapons. Most prefer the shoulder mounted plasma caster. "
from wikipedia. Pretty much confirming that this is what dallas uses, so it must have some kind of triggering mechanism. (but then again, this was known for the most part anyway)
The term "scatter gun" also seems familiar, as I think its referenced in Aliens vs predator: War.
And then there's this:
"Sonic trap: Used to make loud noise and temporarily paralyze an enemy or prey. "
Maybe this is indeed related to the red lazers seen in the sewer scene. The two aliens may be partially subdued by it allowing wolf to take control of the situation. Apparently its from Predator: Concrete Jungle.