Soo.. what are you gonna do with all thous guns you just stole??? I’ll tell you, your gonna go slaughter The Brotherhood!
After the cut scene of you giving the order to attack the Brotherhood’s hideout, grab a car and head there yourself! Follow the trail to the hideout and meet up with some Saints. Once at the hideout start killing off the marked lieutenants to bring Maero out. Once they are all dead make your way into the hideout, when inside make your way up to the roof killing all Brotherhood in sight. Once on top of the roof get ready for a unfair fight. You will notice that Maero is holding a mini-gun. This is the best strategy with out using cheats: At the beginning of the fight sprint up and leap onto a recessed area in front of him. He cannot hit you when close with the mini-gun but he will change to explosives and start throwing them at you! When he changes run back to where you started and unleash hell on him. If he switches back to the mini-gun do the same thing! keep doing this until he drops.
Once Maero runs out of health the mission is over.