Jim probably fired a few shots, gleefully laughing at the prospect of excitement -- Mars has been boring, so far, hiding from the syndicate, the real criminals, in a goddamn sewers -- but that didn't last long before he realized they were outnumbered and the very, very real threat of returning to prison occurred to him, so he bolted down a dark and suitably creepy pipeline.
Val, in turn, would not have waited for Sawyer (or anyone, for that matter) to catch up before charging headlong after him.