SPOILER ALERT!!!!!!!!
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I think the 3 dudes were supposed to be chaotic demons that used Keaton's obsessive "meddlings" as a portal into this world. A twist on the Ouija board possession. Maybe they represent the voices in the heads of killers and such. Making people do bad things, causing death and destruction. And Keaton stops someone under their influence so they take revenge. That's my guess.
"The nose of a mob is its imagination. By this, at any time, it can be quietly led." - Edgar Allan Poe
"A person is smart. People are dumb, panicky, dangerous animals and you know it." - Agent K