Authorities may never be able to piece together the reason for James DiMaggio's rampage.
"When you get a completely irrational act like we've seen here with two murders and a kidnapping, sometimes you might not be able to come up with a rational explanation," San Diego County Sheriff Bill Gore said
DiMaggio, a 40-year-old telecommunications technician at the Scripps Research Institute, was close enough with the Andersons that the children called him Uncle Jim. At least one of Hannah's friends said DiMaggio told the teenager he had a crush on her, which made her uneasy.
On the night of Aug. 4, investigators said, he asked the family to come to his home in Boulevard, about 50 miles east of San Diego near the Mexican border, so he could say goodbye before he moved to Texas. It was a ruse, authorities said.
DiMaggio killed Christina Anderson, 44, possibly by striking her with a crowbar; authorities discovered her body in his detached garage. They also found DiMaggio's two-story log home engulfed in flames with the body of 8-year-old Ethan Anderson inside.
Apparently, Hannah had been elsewhere on the large, weed-choked property.
"There was just no way that she would have been aware that her mother and little brother were dead," Gore said.