Brian Laundrie's sister urges him to turn himself in, is unsure whether their parents are involved in his disappearance — and says he briefly came home after physical altercation

Cassie Laundrie has urged her brother, Brian Laundrie, to turn himself in after going missing following his girlfriend's murder and said that she doesn't know whether her parents are involved in his inexplicable disappearance.

She also revealed that her brother returned home to Florida — without the late Gabby Petito — approximately five days after Utah police questioned the two about a domestic dispute in which Brian was reportedly seen hitting Petito.

What are the details?

In remarks caught on camera and obtained by News Nation, Cassie said Brian flew to the family's Florida home around Aug. 17 without Petito, but returned to Petito's side before she went missing and was ultimately found dead.

Cassie, who delivered the remarks to a group of people gathered outside her home, said that she visited with her brother during his mid-August visit and that nothing seemed amiss, adding that he did not state that the two got into an argument.

"He was telling me where they were going next," she recalled. "I FaceTimed with Gabby and [my] kids on that trip."

When asked if she believed her brother killed Petito, or if her brother was even alive, she answered, "I don't know."

Elsewhere during the interview, Cassie said that there was a rift between her family concerning the ongoing case.

When asked if she believed that her parents were involved in Brian's disappearance or had an idea on his whereabouts, she responded, "I don't know."

"I am losing my parents, and my brother and my children's aunt and my future sister-in-law on top of this, and you are not helping," she told the crowd. "This is not how we want the world to find out when we're angry and upset. But I can't have my kids crying for three days in a row."

When asked why she felt that she was "losing" her parents, she responded, "[B]ecause they are not talking to us, either."

She added that she had no idea why her parents refused to speak with her or her husband.

"If I knew, I would say," Cassie continued. "I don't know."

Cassie's husband, James Luycx, told those gathered, "The sooner he is found, the sooner this is over for us."

Brian remains a person of interest in Petito's death after her remains were discovered Sept. 19 near a Wyoming park, and there is an active warrant out for Brian's arrest on fraud charges for purportedly using someone's bank card around the time that Petito disappeared.

What else?

Cassie doubled down on her suggestion that Brian come forward, and on Tuesday told "Good Morning America" that if her parents are involved, they also "need to come clean."

During the interview, Cassie said that she simply didn't know "what to think" about what happened between her brother and Petito during their cross-country trip that this was the end result.

She added that if her parents — Christopher and Roberta Laundrie — had anything to do with their son's disappearance, they need to own up.

"I don't know if my parents are involved," Cassie said. "I think if they are, then they should come clean."

She continued, vowing that if she'd heard from her brother, she would have turned him in.

"I really wish he had come to me first that day with the van because I don't think we'd be here," Cassie insisted. "I would tell my brother to just come forward and get us out of this horrible mess."

Cassie added that she waffles between concern and anger, but that at the end of the day, she wants answers.

"I worry about him. I hope he's OK, and then I'm angry and I don't know what to think," she admitted. "I hope my brother is alive because I want answers just as much as everybody else."