The FBI has released photos of doomsday mom Lori Vallow, her two now-missing children, and her brother during a Sept. 8 visit to Yellowstone National Park, and appealed to the public to submit any other video or photos from that day that could be helpful.

The trip may have been the last time that Vallow’s daughter Tylee Ryan, 17, was seen. Her stepbrother, 7-year-old J.J., was last seen Sept. 23.

The hunt for more clues related to the Yellowstone visit comes as Vallow, 46, is scheduled to appear Friday in an Idaho courtroom for a preliminary hearing on charges tied to the children’s disappearance.

She and her new husband, Chad Daybell, have refused to cooperate with the police investigation and she ignored a court order to produce the kids—which resulted in her arrest on charges of child desertion and contempt of court.

The FBI set up a mobile command unit in Rexburg, Idaho, this week and then on Thursday invited people who were in Yellowstone on Sept. 8 “to submit any images, video, or other information that may assist in the investigation.”

The photos the FBI released show Vallow and J.J. mugging for the camera in one shot, and Tylee hugging J.J. while Vallow’s brother, Alex Cox, looked on in another.

Two months earlier, Cox shot dead Vallow’s then-husband, Charles Vallow, in what was initially described as a domestic dispute and a case of self-defense. Cox has since died himself of unknown causes.

Vallow married Daybell, the author of apocalyptic novels for a Mormon audience, in November—weeks after his wife, Tammy, died. Her death was listed as natural after he declined an autopsy, but after the kids vanished, authorities exhumed her body to determine if there was foul play.

In a post on a doomsday prepper forum after Tammy’s death, Daybell wrote that it “came as a shock,” East Idaho News reported.

“I couldn’t believe I hadn’t been awakened somehow, but all indications are her spirit simply slipped away in the night,” he wrote.

The post was titled: “Moving into the Second Half of my Life.”