Onishima is shown to be exceptionally short tempered and slightly maniacal, sending whole armed platoons after the GG's and other gangs, ranging from Officers, to police dogs, to helicopters armed with missiles, to SWAT, to parachutists with machine guns. He himself uses a large revolver to take out gang members. When the Golden Rhino's show up, DJ Professor K specifically says in a cutscene that the police force was "too scared to take on the Golden Rhino's". This may be why Onishima does not appear again after chapter 1.