Delia D'Ambra

Around 3.30 p.m.

on Sunday, October 19th, friends of 20-year-old Brandon Rumbaugh and 19-year-old Lisa Guerreri were walking by a dirt turnaround about two miles off Interstate 17 in rural Yavapai County, Arizona, when they spotted exactly what they'd been desperately wanting to find.

a white 2000 Ford F-150 pickup truck, which was the same color, make, and model that Lisa's mother, Paula Guerreri, owned.

When the friends approached the truck, they peered inside the bed and saw both Brandon and Lisa tucked into their sleeping bags.

At first glance, the couple appeared to be sleeping, but a closer examination revealed something truly disturbing.

They were both deceased.

Initial coverage by the Arizona Republic explained that when Yavapai County Sheriff's detectives arrived on scene, they weren't able to tell right away exactly how the couple had died.

There were no obvious signs of trauma.

However, the Sheriff's Office later walked back that statement when a spokeswoman for the agency clarified that there were signs of physical trauma initially observed on the victims.

But as far as what those traumatic injuries were, the Sheriff's Office didn't immediately clarify.

The following day, Monday, October 20th, the Yavapai County Medical Examiner's Office concluded Brandon and Lisa's autopsies.

And the day after that, authorities announced at a news conference that both victims had died from multiple gunshot wounds to the head, apparently inflicted while they'd been asleep.

Neither of them had drugs or alcohol in their system, and there were no indications that a robbery or sexual assault had taken place.

So from the start of the investigation, the sheriff's office had very few leads to follow.

They knew they were dealing with a double homicide that had taken place sometime Friday night or Saturday morning.

But other than that, clues pointing to a particular suspect or suspects were slim.

For example, investigators hadn't found any shell casings or tire tracks at the crime scene, and initial observations also ruled out a murder-suicide situation.

Now, despite a seeming lack of physical evidence, what authorities did have was a fairly detailed timeline of the couple's last movements and communications.

When they'd left to go camping on Friday evening, Brandon and Lisa told their friends and family members that the plan was to borrow Paula's truck and drive about an hour north of Phoenix to go camping off Interstate 17.

During their drive, Lisa had spoken with her mom because Paula had called to check in and see how things were going.