Logan Tyler Mott was driving a 2015 Dodge Dart - presumably the auto taken from his grandmother - when he was stopped about 7 p.m. Friday on the Peace Bridge, a span at the end of Lake Erie linking the USA and Canada, said Aaron Bowker, the agency's public affairs officer in Buffalo, N.Y.
Jacksonville detectives are calling Logan a person of interest in the death of 53-year-old Kristina French.
The Jacksonville Sheriff's Office believes Mott is in somewhere in the northeastern area of the United States. "No matter what, Logan is our child and we love him and are standing by him to help in any way".
"If you have taken them we are begging you to return Logan and Kristina", she begged in her post.
The teen was spotted on surveillance video in Pennsylvania driving the missing vehicle on Thursday.
Police who later investigated the scene said they found evidence pointed to "possible criminal violence" in the home.
Authorities in Florida began searching for Mott and his grandma, Kristina French, 53, Wednesday after they neglected to get his dad from the air terminal.
Mott's mother, Carrie Campbell-Mott, confirmed that Logan has been detained but is safe and sound, First Coast News reported.
Anyone who sees him is asked to call 911.
Mott was being watched by French at her Neptune Beach home while his father, a Jacksonville Sheriff's Office corrections officer, was on vacation. Logan, however, was still missing and immediately became the number one suspect.
The boy is a student at Sandalwood High School in Jacksonville.
Action News Jax has learned French also didn't show up for work Monday or Tuesday.
"Logan has so many friends and family that are desperate to hear from him", she said.