The pickup truck belonging to the father of two boys who authorities say were kidnapped from their grandmother’s Tampa-area home has been found in a southwest Florida parking garage, but the two boys, whose disappearance was posted on metro Atlanta interstate message boards Thursday, are still missing.

According to a press release from the Hillsborough County, Fla., Sheriff’s Office, Joshua Hakken, 35, entered the grandmother’s home around 6:30 a.m. Wednesday, tied the grandmother up and removed his sons, 2-year-old Chase Hakken and Cole Hakken, 4.

Florida authorities issued an Amber Alert for the boys Wednesday night, saying they could be traveling in a black 2006 GMC Sierra pickup truck owned by their father. That truck was later found in Madiera Beach, Fla.

The boys’ mother, 34-year-old Sharyn Patricia Hakken, was also listed by the sheriff’s office as a suspect in the boys’ abduction.

The Tampa Bay Times reported that Joshua Hakken lost custody of his sons last year after a drug possession arrest in Louisiana.

“Both suspects are anti-government and have attempted a previous abduction at gunpoint in Louisiana,” the sheriff’s office said in the press release. Both are believed to be armed and dangerous.

The Associated Press contributed to this article.