UPDATE 11/24/17 11:16 pm: JSO says Logan Mott has been detained by US Customs and Border Protection, as he tried to enter Canada from the Buffalo, New York area. ORIGINAL STORY: It's a tragic update in the days-long search to find a missing 15-year-old and his grandmother. The Jacksonville Sheriff's Office announcing Friday afternoon they do believe foul play was involved, as they've recovered what they believe to be the body of 53-year-old Kristina French in the backyard of a Neptune Beach home connected to the two. 'The burial site was excavated today and human remains were located. They appear consistent with the description of Kristina French, but there will be no positive identification until the autopsy is completed by the medical examiner,' says JSO's Director of Investigations, Ron Lendvay. At this point, JSO says 15-year-old Logan Mott is still missing, as is the silver Dodge Dart. Police say they do believe Mott is alive and in that vehicle. 'We have video surveillance of an individual we believe to be Logan Mott, with what we believe to be the car that's missing in this case, in south central Pennsylvania yesterday at 1:15 pm,' says Lendvay. JSO says they're in the process of obtaining an arrest warrant for Mott for auto theft. He's also considered a person of interest in connection to the death of the person found in the backyard of the home on Seagate Avenue. Police say Mott may also be in possession of firearms, as guns had been reported missing from that home, so if you do see him, you’re urged to call 911.