My thoughts... Murderer had Mac at the crime scene (which has yet to be discovered) Killing occurs. Murderer calls for help to move her vehicle. Calls jailed bros. One drives Macs car to PC. Other brother follows to PC. Gets a call from murderer on way saying to check for her cell phone so car can't be located quickly. Reaches into her purse and finds cell phone and shuts it off. Gets in car with brother and heads back to town. Meanwhile murderer has left Mac at crime scene. He leaves briefly to go to spec house and get a tool. Goes back and does whatever he does to Mac.
prepares her body for transport to CB. Cleans scene up and tool. Returns tool to spec house and enters via garage. Leaves a partial bloody footprint on floor which is later found when LE enters home.
Takes her body in the dark and places it where it is located.
Vehicle is located and dusted for prints. LE notices seat is too far back for Mac to have been driving, so they assume someone drove her car there. Prints are a match in the data base for a jailed convict brother. One brother is brought in on print discovery. Won't talk. Second brother is brought in because he missed his court date the prior week. Brothers are not cooperating. Both are being held on no bail. Murderer should have bruises cuts scrapes markings or something on him. Even if it was a clean kill, the after work would have been messy. Delivering the body in the dark and hauling up and down hills, in sticky bushes etc. perp should be injured to some extent.
It is only a matter of time.