Brian Laundrie's sister urges him to 'come forward' amid nationwide search

Brian Laundrie's sister, Cassie Laundrie, spoke to ABC News for an interview airing Tuesday on "Good Morning America."

Cassie Laundrie said she has a message for her missing brother, who has been the center of a nationwide manhunt after the body of his girlfriend, Gabrielle "Gabby" Petito, was found in Wyoming last month.

"I would tell my brother to just come forward and get us out of this horrible mess," Cassie Laundrie told ABC News in an interview airing Tuesday on "Good Morning America."

Brian Laundrie, 23, and Petito, 22, were traveling across the country this summer in Petito's white 2012 Ford Transit and were documenting their road trip on social media. On Sept. 1, Brian Laundrie returned to his parent's home in North Port, Florida, by himself in Petito's van, according to authorities. Petito was reported missing on Sept. 11 by her family in Long Island, New York, authorities said.

Cassie Laundrie, who lives in Florida with her husband and two sons, told ABC News that her brother and parents stopped by for a visit the day he returned.