The teen went before a judge for the second time Thursday, and is expected to have another hearing in 10 days.
This morning, the judge said she believed the suspect would be a danger to himself or the community and sent him back to juvenile detention.
The suspect will return to juvenile court every 10 business days so a judge can determine if he should be released or remain behind bars.
The judge in the case is forbidding us from reporting the suspect's name or taking video of him in court due to his age.
VIDEO: Teen's rape and murder caught on cell phone
The suspect's attorney Jerry Michael Acosta, tells Eyewitness News, "This is an ongoing investigation that is in it's very early stages, so we ask that the public reserve judgement until all the evidence is collected and evaluated."
Family members for the teen were also there during the hearing, but would not speak with abc13.
We now know the disturbing details of what happened the day Perez was murdered.
Court documents detail the events that lead up the murder.
Prosecutors say last Friday, Karen's 15-year-old boyfriend sent a text message to Perez ordering her to skip class at a South Houston High School and meet him at near by tennis courts. If she did not, investigators say he threatened to kill her.
Surveillance video from a local taqueria shows the two leaving hand in hand.
Court documents accuse the boyfriend of raping and strangling Karen and recording it all on his cell phone.
When she told a him 'no,' investigators say she called her by name then allegedly strangled her inside an abandoned apartment complex.
Her last words on the recording were "I don't want to die."
According to court documents, after the girl was reported missing the suspect and his father went looking for Perez but during their search the suspect allegedly told his father Perez was already dead.
Neighbor Alexandria Hernandez says she is appalled by what happened.
"It's heart breaking as in like because she was so young and I mean nobody deserves to have their life taken away like this," Hernandez says. "My deepest condolences to the family, and I am sorry that this had to happen to you, such a beautiful girl."