I find it hard to believe that the Matta gun was put to use at the jail / prison. There is no reason to rely on a clunky, rather inaccurate prototype in my opinion unless there has been a good reason to do so. Puck and the others were on a recon mission, these guys know exactly what to do and what to do not. So, here is my theory - they either triggered a booby trap at the jail, or they unfortunately ran into a group of mallers or both. I think that it is not unlikely that Puck was held at gunpoint while he was communicating with the safe house.