Don't shoot the lady who spawns on the 3rd map (bridge level ) near the blue keyboard. She will help you fight the monsters.
Otherwise this is a straightforward single player adventure in chaos as the city erupts in civil unrest
A wild man from the jungle reluctantly entered the big city at his parents' request that he find a career path. Once there, he found nothing but dead ends, homelessness, drug addicts & demons & piles of fecal waste ( ( YUCK!! ))
Fortunately now the rules of society have been flushed down the proverbial waste drain & the cities erupt on free for all lawless chaos. For some untrained in instinct this is pretty scary but now jungle boy's having a new adventure. POTUS called in martial law but the military quickly said "f**** this" & joined with the air forces to fly away to vacation island, leaving the leftover survivors to juggle resources amidst their selves. Now it's up to you to survive & seek transport back to the mighty j7ngle away from the smog & grime of human clutter
Good luck