The 14-year-old boy charged with murdering a 13-year-old cheerleader Tristyn Bailey was held in custody on Tuesday morning for another three weeks while prosecutors decide whether to charge him as an adult and police revealed more of their case against him.

Aiden Fucci, 14, was been named by police as the suspect in the killing of 13-year-old Tristyn Bailey.

On Sunday night, he took a selfie in the back of a cop car which he then posted on Snapchat with the caption 'Hey guys has inybody (sic) seen Tristyn lately'. It was before her body was found in woods.

Now, police say they will use that 'egregious' selfie as evidence against him and that it proves he was 'proud of what he did'.

'I know it looks egregious with him making those statements in that car, but that is now evidence that we gather and use against him. So that just makes our case a better case to present to the State Attorney’s office and to present to a jury down the road saying this was his mindset.

'This is what he’s doing, was he’s proud of what he did. So, you know, this is going to help our case and make it stronger to, you know, his intentions,' St. Johns County Sheriff Robert Hardwick said in an interview on Tuesday with local outlet WOKV before Fucci's first court appearance.

On Tuesday, Fucci appeared via Zoom before Circuit Judge Michael Orfinger, who said there was probable cause to charge him in Tristyn's death. He held him in custody and gave prosecutors until May 31 to decide whether or not to charge him as an adult.

In the meantime, Judge Orfinger banned photos of Fucci in his courtroom.

The teenager appeared in a black jail sweatshirt. He looked relaxed throughout the hearing and put both of his hands behind his head at one point.

His parents Jason Fucci and Crystal Smith were both on the call. They spoke briefly to confirm that they had hired him a lawyer.

None of Tristyn's relatives spoke during the hearing.

Her cousin told The Sun that she hopes Aiden confesses to killing her.

'I have cried my eyes out... I'm happy they made an arrest and hope they try him as an adult.

'Tristyn was a sweetheart, she loved cheerleading, I'm an emotional wreck, my husband and I didn't sleep well last night,' Connie Stull said.

Tristyn's body was found in woods on Sunday night, less than 12 hours after her family reported her missing.

It's unclear how she died but police say her body was found fully clothed - she was wearing a dark top and white cheer skirt.

She was last seen at 1.12am on Sunday, and was reported missing at 10am. She and Aiden were classmates at Patriot Oaks Academy.

'We have arrested a suspect by the name of Aiden Fucci, 14 year old. He is currently in custody charged with second degree murder.

'This is a long process, we're in the very early stages of this.

'The suspect is in custody - there are no further threats to this case,' Sheriff Robert Hardwick said at a press conference on Monday morning.

Police have not shared any more information about the kids, including what they were doing on Saturday night before Tristyn vanished.

After she was reported missing, dozens of local volunteers joined in the search for her.

The man who found her body was one of them - police say he'd seen on the news that she was missing and went out to look for her.

She was last seen at the Durbin Amenity Center in St John's at 1.15am. It's unclear what she was doing there or if Aiden was with her.

The center has an outdoor pool and tennis courts. It is next to a lake and there are woods nearby.

In a statement on Monday afternoon, a spokesman for the state's attorney's office said: 'As Sheriff Hardwick stated in his press conference today, our office will continue to investigate the case to determine both the appropriate charges going forward, and whether or not (Fucci) will be charged as an adult.'