Brian Laundrie's sister has delivered a very public message to her infamous brother.
Cassie Laundrie spoke out for the first time since the disappearance of her sibling on Tuesday, speaking to Good Morning America about the death of Gabby Petito and her brother's alleged role in this tragedy.
"I worry about him. I hope he is okay," Cassie said in this interview.
"I'm angry and I don't know what to think. I would tell my brother to just come forward and get us out of this horrible mess."
Brian Laundrie, of course, has been missing for weeks.
On September 21, his girlfriend, Petito, was confirmed dead after the couple had been traveling across the country, recording the trip via videos that Gabby uploaded to her popular YouTube account.
The confirmation came 18 days after authorities say Laundrie returned to his parents' Florida home in Gabby's car -- but without Gabby by his side.
After Petito's parents reported her missing on September 11, Laundrie left the Florida home on September 14... and hasn't been seen since, his parents told authorities.
According to Cassie, the last time she spoke to her brother and saw him was eight days before he vanished when their family went to Fort De Soto Park in Florida's Pinellas County.
"We just went for a couple of hours and we ate dinner and had s'mores around the campfire and left, and there was nothing peculiar about it," she told GMA.
"There was no feeling of grand goodbye.
"There was no nothing."
Thus far, authorities have not explicitly connected Laundrie to Petito's death.
However, he is a person of interest and is considered a flight risk, in part due to a federal arrest warrant accusing him of illegally using another person's debit card.
A coroner made an initial ruling last month that Petito's death was a homicide.
Moreover, recently-released bodycam footage from a 911 call on August 12 -- placed by an onlooker who claimed he/she witnessed Laundrie assaulting Petito -- appears to depict the abuse Gabby suffered at the hands of her boyfriend.
Brian's parents, Chris and Roberta Laundrie, said they have not seen their son, who lives with them in North Port, Florida, since September 14.
Prior to her passing, Gabby also lived with the family.
According to Cassie, she has cooperated with authorities and hopes her loved ones all do the same.
"I have been in touch with law enforcement," she said in ABC.
"Justice for Gabby would look like having someone come forward and tell the truth.
"I don't know if my parents are involved.
"I think if they are, then they should come clean."
In a previous statement to E! News, the Laundrie family lawyer said Chris and Roberta do not know where Brian is right now.
"They are concerned about Brian and hope the FBI can locate him," the attorney said.
"The speculation by the public and some in the press that the parents assisted Brian in leaving the family home or in avoiding arrest on a warrant that was issued after Brian had already been missing for several days is just wrong."
In another previous statement, Brian's attorney addressed the warrant that his client "knowingly and with intent to defraud, used one or more unauthorized access devices," including a debit card, via this message:
"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.
"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."