Florida cheerleader Tristyn Bailey was stabbed multiple times in a 'horrific, cold blooded murder', the sheriff investigating her death revealed on Tuesday.

The 13-year-old was found dead in St Johns on Sunday less than 24 hours after her family reported her missing.

Police have arrested and charged 14-year-old Aiden Fucci with second degree murder. He is in juvenile custody and prosecutors are yet to decide whether to charge him as an adult.

On Tuesday, St. Johns County Sheriff Rob Hardwick told local network NewsJax that Tristyn was killed violently, stabbed multiple times.

'This is a cold-blooded murder of a 13-year-old young girl who did not deserve to die.

'I don't want to mention the number of times, but it is horrific. It is horrible. And the word accident is nowhere involved in this case,' he said.

He has still not determined the motive for the killing.

'We're going to look at every aspect, every crime that's out there. Our guys and girls are going to leave no stone unturned,' he said.

Before Fucci made his first appearance on Tuesday, Sheriff Hardwick said he was 'proud' of killing her.

On Sunday night, before cops found Tristyn's body, Fucci was hauled in for questioning.

While in the back of the patrol car, he posted a selfie on Snapchat, flashing a peace sign, with the caption: 'Has anybody seen Tristyn lately?'

Hardwick called the taunt 'egregious' and said it added to the evidence that Fucci wanted to kill her and was remorseless over it.

'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.

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.'