Hillsborough County Sheriff's officials are becoming more concerned for the safety of two young boys they say were taken by their father Wednesday in Tampa.

The 2006 GMC pickup truck belonging to the family has been located abandoned in the John's Pass Parking Garage located at 12901 Gulf Blvd in Madeira Beach.

HCSO detectives as well as crime scene technicians are on scene and will now carefully process the vehicle in John's Pass.

An Amber Alert was issued Wednesday for the boys, 4-year-old Cole Hakken and 2-year-old Chase Hakken.

Authorities say their father, 35-year-old Joshua Michael Hakken, entered his mother-in-law's house in north Tampa, tied her up and left with the children Wednesday afternoon.

The Sheriff's Office has set up a command post at its Falkenburg Road office to receive calls and tips regarding the case.

The children's grandparents were expected to speak at a news conference at noon but cancelled at the last minute, saying the situation is too emotional to them.

Former foster father speaks out

A man who provided foster care for Chase and Cole Hakken had trouble talking about the children he calls amazing.

"I can still see the little one looking up at me and saying "big hug, big hug," he said.

The man doesn't want to be identified for safety reasons.

The Hakken brothers were put in his care after their father, Joshua, was arrested in Louisiana on drug charges following some sort of anti-government rally.

He said he saw a violent side to the Hakkens when he says Joshua Hakken threatened them with a gun.

"The parents showed up at my house. My wife would not let them come through and they wound up pulling out a gun on her and once they pulled a gun on her, my wife called the cops and when we called the cops they took off," he said.

Custody of the boys was eventually given to their maternal grandmother, but for the few weeks they lived with him, the foster dad says they were very well-behaved.

"They listened. They were a joy to be around," he said. "They were doing for us, we weren't doing for them. That's what it felt like."

Car found in Madiera Beach

Officials said the 2006 GMC pickup truck has been located abandoned in the John's Pass Parking Garage in Madeira Beach.

The children's mother, 34-year-old Sharyn Patricia Hakken, is now believed to be with them.

The Tennessee Bureau of Investigation has issued a statewide alert after the car was believed to be seen in southeast Tennessee.

Chase Hakken is 3 feet tall, weighs 33 pounds, has brown hair and brown eyes.  He was last seen wearing pajamas. Cole Hakken is 3 feet 9 inches tall, weighs 44 pounds, has brown hair and brown eyes.  He was also last seen wearing pajamas.

Deputies spent Wednesday afternoon and evening at the parents' home, searching for any clues that might indicate where they would go. Detectives said the parents should be considered armed and dangerous.

Anyone with any information is asked to call 911 or to call the Hillsborough County Sheriff's Office at (813) 247-8200.

Previous attempt to take the children, officials say

According to authorities, Hakken was previously involved in an attempted armed abduction of their children in Louisiana.

Officials said they have so far been able to determine that Joshua Hakken was arrested in a hotel on multiple drug charges in St. Tammany Parrish, Louisiana, where he had just attended some type of anti-government rally.

Slidell police say were called to the hotel in June in reference to a disturbance involving Mr. and Mrs. Hakken. Police say when they arrived the parents were acting in a bizarre manner that alarmed officers.

Police say they were talking about “completing their ultimate journey” and were traveling across the country to “take a journey to the Armageddon.” Police say both of the children were present in the hotel at the time.

Police say based on the parents’ behavior and the fact narcotics and weapons were inside the hotel room, officers called the Office of Child Services, who determined the children were in danger and needed to be taken into custody and temporarily placed in a foster home.

"This is not really about anti-government at this point," said David Couvertier, FBI. "Individual beliefs, people in our country should believe in whatever you want to believe in. It's the manner in which the kids have been taken is what concerns law enforcement and the reason we've taken the steps we have taken."

Joshua Hakken was placed under arrest and charged with possession of marijuana, possession of drug paraphernalia, and the use of a controlled and dangerous substance in the presence of minors. Officers also took custody of the guns.

Two weeks later, police say they were notified Joshua Hakken had shown up at the foster family home with a firearm demanding the return of his children. The foster parents called 911 and police say Hakken fled without his children.