Brian Laundrie left home without his phone and wallet last week before going completely off the grid, a source close to the family said.
The source told CNN's Chris Cuomo on Thursday that Laundrie, now the center of a nationwide manhunt after the highly publicized murder of his fiancé Gabby Petito, left his parents' home last Tuesday in a panic state and that they feared for their son's safety.
While the FBI is yet to make a comment, Laundrie's parents, Christopher Laundrie, 62, and wife Roberta, 55, have become the target of investigators since their son's suspicious disappearance.
FBI agents secretly tailored Laundrie's parents as they drove 240km from their North Port, Florida, home to Orlando to meet with their lawyer on Thursday.
Reports claimed undercover agents followed the couple into the Orlando Public Library on Thursday.
Though it's not clear what the pair were doing in the library, the couple did meet with lawyer Steve Bertolino in Orlando during their trip.
In a statement released last week, Bertolino revealed that Laundrie would not be speaking to investigators due to the fact that 'intimate partners are often the first person law enforcement focuses their attention on in cases like this.'
Bertolino argued in his statement that any comments made by his client to police could be used against him, 'regardless of whether my client had anything to do with Ms Petito's disappearance.'
'As such, on the advice of counsel Mr. Laundrie is not speaking on this matter,' asserted the attorney.
Neighbors also said they spotted Laundrie and his parents packing an 'attached camper' used for their long-weekend camping trips ten days after he returned to the North Port residence without Petito, on September 11 the day Gabby was declared missing.
Lundrie has since vanished, after his fiance's body was discovered by investigators last Sunday.