SCOTTSDALE, AZ — Unsolved, but not forgotten.
Twenty years after the brutal murders of a Scottsdale mother and her two children, the prime suspect remains one of America's Most Wanted fugitives, but the million-dollar question that is still unanswered today -- is Robert Fisher dead or alive?
Different detectives have different theories, but they continue to keep the investigation open, and look into every tip that comes their way.
FULL COVERAGE: Is Robert Fisher dead or alive 20 years after Scottsdale killings, house fire?
"This is by far the most heinous crime that we've had here in Scottsdale," said Scottsdale police detective John Heinzelman, who heads up the 20-year-old murder investigation today.
The brutal crimes took place in 2001. Police believe Fisher killed his family due to marital problems and the fear of divorce, then fled. The murders were especially heinous.
"To take a knife and slaughter your children, to slash their throats, then ultimately slash your wife's throat. That is a different level. That is up close and personal," said Heinzelman.
Home videos released by police show happier days for the Fisher family. Hours upon hours of footage show birthday parties, dance recitals, and carefree times playing in the family's backyard. But those who knew Robert Fisher say, all was not what it seemed.
"They were having marital difficulties, I guess that's about the most I would say," said Pastor Gregg Cantelmo, who counseled the couple.
"The motive is probably the $64,000 question when you look at it," added Detective Heinzelman.
The family's bodies were discovered in the charred rubble after police say Fisher rigged up his natural gas line to explode during a house fire.
The last known picture of Fisher was captured at an ATM where he withdrew $280 the night before the murders, according to police reports.
Ten days later, police would find the final big clue in this case.
Mary Fisher's vehicle, abandoned in the Tonto National Forest near Young, Arizona. The family dog was found alive by the vehicle.
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Despite a massive search, there was no sign of Robert Fisher.
To this day, officials wonder if he managed to escape and start a new life somewhere, or if he died out in the wilderness and has just not yet been discovered.
RELATED: What police believe Robert Fisher looks like today
Friends said the Tonto National Forest was a well-known terrain for Robert Fisher. He camped, hiked, and hunted in the area. Some even considered him a "survivalist" who knew how to live off the land. He was familiar with the huge network of caves and caverns that dotted the remote and rugged landscape.
Scott Wood, an archaeologist who worked for the Forest Service for 40 years said he would not be surprised if Fisher had died in the forest.
"People have been able to get lost and die out there and not be discovered for some years. There's plenty of space out there," said Wood.
A large part of the forest land was located in the Apache Indian Reservation where search crews in the area had no jurisdiction. Wood described the area as very remote and without roads.
"He could go for miles there without being seen by another human being," said Wood.
Like many though, Wood believed Fisher was dead.
"Usually if somebody is trying to do something like that, they're leaving a trail of broken-into houses and stolen vehicles. You're not going to walk to Canada. You're going to leave some trail of criminal activity on the way," said Wood.
Former county attorney Rick Romley, who filed charges against Fisher in 2001, agreed.
"My supposition is no, he is not alive, but you know you don't close the case because you never know," said Romley.
Scottsdale police said they were getting new tips in this case almost on a weekly basis and they looked into every single one of them.
