been missing for weeks. and tonight the police and f.b.i. are still searching for her fiancé. cbs' jericka duncan is following new developments tonight in florida. >> police, search warrant! >> reporter: f.b.i. agents descended to the florida home of 23-year-old brian laundrie. they were in and out of the home for more than eight hours, questioning his parents and collecting evidence that might tell them what happened to petito and where laundrie is. the manhunt led them to a nature preserve but investigators found nothing. >> gabby petito never goes outside. >> reporter: the couple left in early july on a cross country road trip documenting their travels on a blog called "van life." but this 911 call came in august. >> reporter: this led to this exchange in utah. >> (crying) we were fighting all morning, and he wouldn't let me in the car. >> reporter: there were no arrests. the couple said they were headed to grand teton national park in wyoming and nearby, this