The family ofBrian Laundriebelieves he is still in Florida — and is holding out hope that he is safe.

“They are concerned,” Laundrie family attorney Steve Bertolino tells PEOPLE, “but hopeful that he is found alive.”

Gabby Petito

Police believe the relationship between Petito and Laundriebecame more strained during their tragic road trip, according to a newly unsealed search warrant connected to the case.

Petito’s best friend, Rose Davis,tells PEOPLEthe couple’s relationship was “toxic,” and that Laundrie had “jealousy issues.”

Gabby Petito, Brian Laundrie

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For now, the FBI is trying to piece together Laundrie’s actions for the past month, including afamily camping tripon Sept. 6 and 7, as well as anew phonehe purchased after Petito went missing.

Also in question: Laundrie’s last contact with his sister, Cassie, who was at the campground with the family on Sept. 6, Bertolino confirms to PEOPLE.

Bertolino says Cassie saw Brian twice after his return to Florida after Petito went missing — once on Sept. 1 and again on Sept. 6.

In an interview withGood Morning Americathat aired Sept. 17,Cassie said of Brian, “I haven’t been able to talk to him. I wish I could talk to him.”

Gabby Petito and Brian Laundrie

However, the time frame to which she’s referring is unclear from the portions of the interview shown onGMA.

If you have information on this case, call 1-­800-­CALL-­FBI (225­-5324).

If you are experiencing domestic violence, call the National Domestic Violence Hotline at 1-800-799-7233, or go to thehotline.org. All calls are toll-free and confidential. The hotline is available 24/7 in more than 170 languages.

source: people.com