Brian Laundrie likely died just two days after his fiancé Gabby Petito was reported missing by her mother, police believe.
North Port Police spokesperson Joshua Taylor said "there is a very good possibility" the 23-year-old fugitive died on September 13 the same day he told his parents he was going hiking in Carlton Reserve but never came home.
Two days earlier, on September 11, Gabby was reported missing by her mother in New York.
The 22-year-old vlogger had been on a cross-country road trip with Laundrie when she vanished sometime around August 27.
Laundrie returned home to Florida alone on September 1, offering no explanation for where Gabby was, and immediately retained an attorney.
Investigators began monitoring him on September 12, secretly planting cameras around his parents' home.
On September 13, North Port Police watched Brian leave his parent's home in his grey Mustang, Taylor said.
Two days later, investigators thought they saw him return to the family home in the same car.
Amid increasing media attention, North Port Police Chief Todd Garrison told reporters on September 16 that police were confident about where Brian was.
"All I'm going to say is I know where Brian Laundrie is at," Garrison said during a press conference.
However, the next day, Brian was reported missing by his parents who said they hadn't seen him since September 14. That date was later revised to September 13 in a statement issued by the family's attorney.
Laundrie's skeletal remains were located October 20 in Florida's Myakkahatchee Creek Environmental Park, which is adjacent to the Carlton Reserve.
The results of an autopsy on Brian's remains, found near his backpack and notebook, were inconclusive.
His remains are now with a forensic pathologist who is expected to return results in two or three weeks, the Laundrie family attorney said.
Petito, meanwhile, was confirmed to have been strangled to death by a "human force."
Her remains were found in Wyoming's Grand Teton National Park on September 19. Coroners determined that she'd been killed around three to four weeks earlier.
Gabby's family has not yet spoken publicly since Brian's remains were found.