Brian Laundrie reportedly left his parent’s home last Tuesday without his wallet or cellphone, a source close to the family says.
The missing man’s parents Christopher and Roberta were concerned he might harm himself, the source told CNN.
Mr Laundrie has not been seen since leaving his family home in North Port, Florida, on September 14, saying he was going for a hike in the nearby Carlton Reserve.
His parents only notified authorities that he had left the house three days later, sparking a massive manhunt that is now in its seventh day.
North Port Police said they could not comment on the investigation, and referred inquiries to the FBI.
The Independent has approached the FBI for comment.
A massive search operation is being conducted at the Carlton Reserve, a 25,000-acre swampland in Sarasota County teeming with alligators, snakes and other dangerous wildlife.
Law enforcement agencies have deployed drones, dive teams, dog units and all-terrain vehicles to search the “vast and uncompromising” reserve, but have so far found no trace of Mr Laundrie.
Friends have said the 23-year-old is a skilled survivalist.
The US District Court of Wyoming issued an arrest warrant for Mr Laundrie after he was indicted by a grand jury for “use of unauthorised devices,” following Ms Petito’s death.
According to the indictment, Mr Laundrie illegally used a debit card and PIN number for charges totaling more than $1,000.
The accounts which he used did not belong to him, while the transactions took place between the dates of 30 August and 1 September.
“It is my understanding that the arrest warrant for Brian Laundrie is related to activities occurring after the death of Gabby Petito and not related to her actual demise,” Steve Bertolino, an attorney for Mr Laundrie’s family said in a statement.
“The FBI is focusing on locating Brian and when that occurs the specifics of the charges covered under the indictment will be addressed in the proper forum.”