Who made up 'Los Pepes' during the drug wars in Colombia against Pablo Escobar?

I'm reading the very fascinating book 'Killing Pablo' by Mark Bowden, and I never understood who made up the dangerous and borderline psychopathic 'Los Pepes' who murdered almost everyone ociated with Pablo Escobar. Some said it was Delta, some said it was the Colombian military Search Bloc, some said it was Colombian police...any ideas on who they were?