Madeline Soto missing: Mom's boyfriend arrested, considered 'prime suspect' in Florida girl's disappearance

UPDATE: Madeline Soto was killed by her mother's boyfriend, Stephen Sterns, Orange County Sheriff John Mina said during a press conference on Friday afternoon. The update comes after five days of searching for the missing teenager. Click here for the latest update. 

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The Orange County Sheriff's Office announced Wednesday that a Florida man had been arrested amid the investigation into the disappearance of 13-year-old Madeline "Maddie" Soto.

Maddie Soto was reported missing Monday night, officials said. Deputies have been following leads, searching neighborhoods and nearby areas of Orlando where she was last seen.

TIMELINE: Everything we know about 13-year-old Madeline Soto's disappearance

Her mom's boyfriend, Stephan Sterns, 37, was arrested Wednesday on unrelated charges amid the investigation into Soto's disappearance, OCSO announced. He has not been arrested or charged in connection to Soto's disappearance, but OCSO said Sterns is the last confirmed person to see Soto – and that he is now considered a "prime suspect" in her disappearance. 

Officials are still looking for the missing girl.

Here is what we know about the case:

Who is Stephan Sterns, and why was he arrested?

Stephan Sterns, 37, is the boyfriend of Jenn Soto, a Central Florida mother whose daughter, Madeline "Maddie" Soto, disappeared earlier this week. He was the last confirmed person to see Maddie on the morning of Monday, Feb. 26, according to OCSO.

Sterns was arrested and booked into the Orange County jail on charges of sexual battery and possession of child sexual abuse material after detectives found "disturbing" images on his phone, OCSO said. They also alleged that Sterns had attempted to delete evidence from the phone.

Stephan Sterns (Orange County jail)

According to OCSO, several sexually explicit images and videos were found on Sterns' cell phone. Detectives said it appears that whatever alleged actions were captured in the images and videos happened at the family's home in Kissimmee, Florida, which is just south of Orlando.

The Kissimmee Police Department will lead the investigation into Sterns' sexual battery case, officials said.

Officials did not elaborate further – and it's unclear if the findings are connected to Soto's disappearance.

Orange County Sheriff John Mina: "We will not stop until we find her"

Sterns was interviewed at OCSO Central Operations on Wednesday by detectives from Kissimmee Police and Orange County Sheriff's Office.

Investigators said he invoked his right to an attorney and declined to speak further. He was arrested on the charges listed above and booked into jail. 

Who is Maddie Soto?

Madeline "Maddie" Soto was last seen on Monday, Feb. 26, one day after she and her family celebrated her 13th birthday.

Maddie’s mother, Jenn Soto, said surveillance video showed Maddie hanging out in the Peace United Methodist Church parking lot after being dropped off for school, but she never made it inside.

"I’m trying to hope for the best, but I’m scared for her," she said. "I want her to be okay; I want her to be safe… I don’t want her to come back harmed. I just want her back – whatever that means, I just want her back."

RELATED: Florida mom begs for daughter's safe return home

Sheriff Mina said deputies attempted to use a piece of Maddie's clothing and a bloodhound to track the girl's scent. However, she was not found. 

According to Soto, her daughter had never run away before. She said the teen had forgotten her cell phone at home that morning, but that was normal.

When deputies searched Maddie's phone, they learned that Soto had told her friends that she wanted to "live in the woods" after her birthday.

The Florida Department of Law Enforcement said Maddie is "endangered," meaning that her physical safety is in danger, such as a predatory abduction or kidnapping.

When was Maddie Soto last seen? 

During a news conference on Wednesday, Orange County Sheriff John Mina said Soto was dropped off a few blocks from Hunter's Creek Middle School on Monday morning by her mother's boyfriend. However, when Soto's mom went to pick her up, she found out her daughter had never set foot inside the school that day.

Sheriff Mina said Soto was dropped off near Peace United Methodist Church on Town Loop Boulevard, a half-mile from the school. 

It remains unclear why she was dropped off at this location, but Sheriff Mina said she was possibly "embarrassed" by her vehicle and asked her mom's boyfriend to be dropped off there.

"Why not drop her off at the school?" Sheriff Mina asked during Wednesday's press conference, adding that the sheriff's office is looking into it.

Sheriff Mina said that the woods behind Hunter's Creek Middle School are among the areas deputies have been searching in. Over 100 personnel, including deputies, detectives, intelligence analysts, specialized personnel, and bloodhounds, have been deployed to help search for the missing teenager.

Deputies and Soto's family continue to pass out flyers in the area to notify people of the ongoing search.

"This is every parent's worst nightmare. We can't even imagine the pain and anguish that Madeline's family is going through," Sheriff Mina said. "We will not stop until we find her." 

Can you join the search?

The Orange County Sheriff's Office thanked those wanting to help search for Madeline Soto but asked the public to avoid entering the search area. 

"For now, we are asking that people refrain from coming to the search area, and to let our Emergency Response Team handle that. But we will advise if that changes," the sheriff's office wrote on X. 

Have you seen Madeline Soto? How you can help

Madeline "Maddie" Soto is a 13-year-old girl who was reported missing this week. She was reported missing on Tuesday after she was last seen at around 8:30 a.m. on Monday, Feb. 26, in the area of Town Loop Boulevard and Hunter's Park Lane in Orlando.

She had just celebrated her 13th birthday with her family over the weekend, her mother, Jenn, told FOX 35.

Soto is a 5-foot-1, 110-pound girl with blonde hair and blue eyes. Officials said she was last seen wearing a green jacket, black shorts, and white Crocs. She has a mole on the left side of her nose and the right side of her chin.

Contact the Orange County Sheriff's Office at 407-836-HELP if you have information about Soto's disappearance or whereabouts.