The morning of March 31, 2023, for Megan Kingsbury began with a funny text exchange with her younger sister, 26-year-old Madeline “Maddi” Kingsbury, who lived in Winona, Minnesota. But that would be the last communication, Megan Kingsbury says, she would ever have with her sister.

Later that evening, Megan Kingsbury says her mother, Krista Naber, reached out to see if she had spoken to her sister recently because Naber had not heard from Maddi Kingbsury in hours. Megan Kingsbury says she wasn’t worried at first, but then Maddi Kingsbury did not respond to her new messages or phone calls either.  “…regardless of how busy she was or what she had going on, she always got back to us,” Megan Kingsbury told “48 Hours” correspondent Peter Van Sant. Her interview is featured in “The Disappearance of Maddi Kingsbury,” an all-new “48 Hours” airing Saturday, April 13, at 10/9c on CBS and Paramount+.

Megan Kingsbury and her family quickly became concerned about Maddi Kingsbury, a mother of two who worked as a clinical research coordinator for the Mayo Clinic. Since most of the immediate family lived hours away from Maddi Kingsbury, they reached out to her friends who lived closer. Megan Kingsbury says she contacted Adam Fravel, who lived with Maddi Kingsbury and was the father to her kids. She says Fravel told her he was also concerned because he had not heard from her either. Fravel told Megan Kingsbury he was at his parents’ home with the kids nearly an hour away. Megan Kingsbury asked Maddi Kingsbury’s close friend, Katie Kolka, who also lived in Winona, if she could check on her sister. Kolka told Megan Kingsbury when she got to Maddi Kingsbury’s home, it was dark and no one was there. But, she says, Maddi Kingsbury’s vehicle was parked in the driveway.

The next morning, on April 1, Megan Kingsbury and the family filed a missing persons report with the local police department. As the investigation took off, Megan Kingsbury had an idea for how she could help find her sister. 

“So I took to social media, TikTok mainly … I had seen tons of videos of people calling for help for, for something in some way and you can get a lot of traction with that,” she told Van Sant.

One of Megan Kingsbury’s first posts — showing her freshly out of the shower, wrapped in a towel and appearing panicked — asked her followers a simple request, “TikTok, I need you to do your thing. This is my sister Madeline Kingsbury. She’s missing…help us find her.” 

That post would eventually get over a half million views on the app. “And I got flooded with messages from people every day,” she said.

Megan Kingsbury says responses came far and wide, including from other countries. She told Van Sant that when she asked her followers to call the tipline if they had any information about her sister to share, so many people called that “… they had to bring in extra help just to go through all the tips that came in.”

In one of the searches, nearly 2,000 people volunteered to help look for Maddi Kingsbury, allowing authorities time to search new locations.

While Megan Kingsbury was spreading the word about Maddi Kingsbury’s disappearance, investigators were reading text messages, reviewing surveillance footage, interviewing family and friends and monitoring tips. One tip, according to a search warrant, came in 10 days after Maddi Kingsbury vanished. A neighbor of Fravel’s parents told investigators their trail camera captured Fravel riding the family’s utility terrain vehicle with a shovel on its bed on the neighbor’s property. When investigators seized the vehicle, cadaver dogs alerted to a scent on the shovel. Cadaver dogs, according to the search warrant, are trained to ignore live human and animal scents, and only indicate human remains.

Fravel’s family told “48 Hours” that there is an innocent explanation for the dogs. They say Fravel’s dad used that shovel to move a dead raccoon the previous weekend.

During the search, Fravel released a statement through his attorney that read in part, “I have cooperated with law enforcement at every turn … I did not have anything to do with Maddi’s disappearance. I want the mother of my 5-year-old and 2-year-old to be found and brought home safely.”

On June 7, 68 days after Maddi Kingsbury was last seen and heard from, a deputy found human remains in a culvert along a dirt road less than five miles from Fravel’s parents’ home and nearly an hour from Maddi Kingsbury’s home in Winona. Maddi Kingsbury’s family was notified by the medical examiner that they were certain the remains were of her.

“I was on the floor and like screamed, crying…what do you say when somebody tells you something like that? There’s nothing that you can say,” Megan Kingsbury told “48 Hours.” 

The next day, authorities notified the public that the remains were a match. But there was another development. Fravel was arrested and charged with Maddi Kingsbury’s murder. According to the autopsy report, the official cause of death was homicidal violence.

In a few emotional posts on TikTok, Megan Kingsbury shared the devastating news with her followers. “…the whole situation is just so sick,” she said in one of the posts.

Fravel is currently being held on a $3 million bail and awaiting trial. “I believe Adam 150% that he is innocent, that he didn’t do this,” his sister, Theresa Sis Mejía, told “48 Hours.” Fravel continues to deny any involvement with Maddi’s death and his lawyers are fighting the charges.

Despite the tragedy, Megan Kingsbury says she is using her TikTok platform to share her process of grieving in hopes it will help others. “I think it’s important to share your grief journey … I’ve gotten a lot of messages from people who’ve gone through something similar, and it’s helped them kind of face their own grief and, I guess, feel freer to share it with other people,” she said.