He never went for the random weaker enemy. He was searching for his other lost gun when he was suddenly ambushed by another left-over statue.
Well... pretty much everyone is dead now besides Kato, Kei and the dog (but with what did that animal ever help out with huh).
One thing that confuses me though is that nerdy guy with the glasses. I never saw him die and he just disappeared after asking for Kishimoto's gun. So assuming that he didn't die off-screen, he's probably hiding somewhere or about to reappear again with a counterattack. It's either that, or Kato killing that end boss himself.