SAN DIEGO (CBS 8) - He wrote a book on the McStay case, but an investigative author is expressing shock over the tragic new twist in the case.
Joseph and Summer McStay vanished from their Fallbrook home more than three years ago.
Monday, their bodies were found in the desert near Victorville, their two young boys are believed to have been buried with them.
The San Diego sheriff's department is lending two investigators to this murder case being handled by San Bernardino authorities.
There aren't any suspects yet - but the man who wrote a book called "No Goodbyes" about the McStay's disappearance has his suspicions.
"Who would kill an entire family with two little children?"
Even for a man who has studied and written about the disappearance of the McStay family for three years - Rick Baker never saw this coming.
"I'm almost grieving myself because I got to know them so well even though I never met them," Baker said.
Friday, authorities confirmed the bones found on Monday in a desert near Victorville belong to Joseph and Summer McStay who had been missing since 2010.
Their two young boys are believed to have been buried in shallow graves with them.
"They're together, and they're in a better place," brother Michael McStay said.
The San Bernardino authorities are handling this now murder case that once relied on a video clip studied by San Diego investigators to suggest the McStays were in Mexico.
"It wasn't them crossing the border. Law enforcement told everybody who will listen it's a voluntary missing case when I knew that it wasn't," Baker said.
Theories about the McStay's fate often include a link to Mexican cartels but Baker is skeptical because of how their Isuzu Trooper was found in San Ysidro.
"If this were some kind of cartel hit like some of my law enforcement sources there are saying, it might have been, but staging the Trooper there is nothing the cartel would have done," Baker said.
The family car was found close to the border but about 70 miles from their Fallbrook home.
"I think whatever happened in Victorville and whoever did it either took the car to the border and went across the border used the car to go down there or it could have been a ruse," father Patrick McStay said.
Whoever killed Joseph, Summer, Gianni and Joseph Junior - deputies vow to find them - although Baker is not sure that will be enough.
"And at this point we just pray for justice. The murderer or murderers I hope are captured and tortured to death," he said.
The author has told Amazon to take his book off its website now that this is a criminal investigation.
Deputies say there is evidence at the grave site that will help find the killer or killers, possibly DNA or fingerprints.