Altruist Cult Camp
$1000 per ped
A Hidden package can be found in the Camp
When you deliver the fourth victim to the Altruist, they turn their guns on Trevor as well and take him inside. He is taken over to a boulder. Trevor notices a wayward Assault rifle and grabs it. He ducks behind the boulder for cover and then the shooting begins.
Use the boulder as cover to pop in and out. There are 5 Altruists who are directly in front of you. You need to get through them carefully. Use the Boulder and Trevor's Rage to deal with them. There are still plenty more to kill. There are at least 11 more that will start coming after you. Keep behind the boulder if the Altruists seem overwhelming. Be sure to use your Sniper Rifle to deal with their Snipers who are up on the water tower. Keep these water towers in mind though. With the second wave and the Snipers dealt with you are in a much better position to advance.
As you head forward, look over to the right and up the water tower there. This one is behind some houses. On top of that tower you will find another Sniper. Gun him down then press forward.
If you want to get the collectible Hidden Package here, you want to find the water tower nearest the front gate. Look on the porch of the shack by it. There you will find body armor and a Hidden package.
You have killed all the Altruists when you get the "Altruist Cleared" message. Just get in your vehicle that's just outside the gate and get back to civilization.