Detectives have found a car belonging to Joshua Hakken, a Florida man who is believed to have kidnapped his two young boys from their maternal grandparents' Florida home after the grandmother was tied up Wednesday, CBS affiliate WTSP reports.

The 2006 GMC pickup truck was found abandoned in the John's Pass Parking Garage, authorities announced Thursday night, according to the station. John's Pass is a fishing village in Madeira Beach.

Detectives believe the 35-year-old Hakken was using the truck to transport his two sons, 4-year-old Cole Hakken and 2-year-old Chase Hakken, after he kidnapped them from their grandmother's home early Wednesday morning, the station reports.

Investigators had to wait for a search warrant before they were allowed inside the truck. When they obtained the warrant, Hillsborough forensics crews reportedly dusted for fingerprints and took photos at the scene.

The truck was then transported to Hillsborough County, where processing of evidence will continue.

The Tampa Bay Times reports that Joshua Hakken lost custody of his sons last year after a drug possession arrest in Louisiana, and that authorities said he later tried to take them from a foster home at gunpoint. The newspaper said the children had been living with their grandparents since last year, and that the Hakkens were informed Tuesday by a Louisiana court that they'd been stripped of their parental rights.

An initial press release identified Joshua Hakken and the children's mother, 34-year-old Sharyn Patricia Hakken, as suspects in the abduction. The news release said "both suspects are anti-government and have attempted a previous abduction at gunpoint in Louisiana."

The investigation and search for the children is ongoing.