Newly released court documents suggest a Massachusetts teen accused of murdering his 24-year-old math teacher may have recorded the killing on his cell phone, reported.

Philip Chism is accused of raping and killing Danvers High School teacher Colleen Ritzer after she asked him to stay after school for help.

The 15-year-old has pleaded not guilty to charges of murder and aggravated rape.

Police say a Massachusetts teen admitted killing the 24-year-old math teacher whose body was found in the woods near the school in October.

In search warrant documents for Chism's phone, state police say Chism admitted killing Ritzer but denied having sexual contact with her.

State police say they want to examine Chism's phone because it is not unusual for people involved in sexually violent homicides to memorialize the deaths "for further humiliation of the victim."

Investigators applying for a search warrant for Philip Chism's phone alleged the 15-year-old may have recorded evidence related to Colleen Ritzer's death on his phone before smashing the device and throwing it away, reported.

Officials claim Chism admitted to killing Ritzer and told them he destroyed both their phones so that he couldn't be tracked.

"I destroyed them so that you would be unable to locate or track me due to the GPS capabilities of the phone," Chism is quoted as saying in court documents.

Investigators said Chism's explanation for destroying his phone seems doubtful, saying it is widely understood that GPS capabilities can be disabled without breaking the device.

Ritzer's body was found with her throat slit and a note reading, "I hate you all."

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The Associated press contributed to this report