New details are emerging about what investigators think happened in the final hours of 13-year-old Janessa Shannon's life.

According to a search warrant obtained by Spectrum Bay News 9, Janessa was beaten and possibly strangled to death — and investigators say it was at the hands of her father, Nahshon Shannon.

Nahshon Shannon is charged with first-degree murder.

For weeks, the Shannon family pleaded for Janessa's return after she went missing from her father's home on July 2.

Nahshon Shannon was the one to report Janessa missing — but not until 39 hours after he said he last saw her.

According to investigators who announced the arrest in early October, Janessa was at a boy's house the night before she went missing. Nahshon Shannon picked up Janessa from her mother's house in Bradenton and brought her back to his home in Riverview.

Janessa's parents had joint custody.

Deputies say Nahshon Shannon sent a text to his girlfriend to leave his house so he can "deal with Janessa."

According to the report, that's not what Nahshon Shannon told Janessa's mother, Michelle Moseley. Nahshon Shannon apparently sent a text message to Moseley that said his girlfriend was with him all night.

However, Spectrum Bay News 9 spoke to the girlfriend, Beena Nair, after Nahshon Shannon's arrest, and she said she was not with him the night Janessa went missing.

"When he brought her back to the house, I was communicating with him via text the whole time. He's like, 'Listen, I just need to talk to her,'" Nair said.

In the days after Janessa’s disappearance, Nahshon Shannon flew to Philadelphia for what he said was business.

"He was like, 'If I don't work, I won't have a roof for her to come home to," Nair said.

"When he brought her back to the house, I was communicating with him via text the whole time. He's like, 'Listen, I just need to talk to her.'" -- Nahshon Shannon's girlfriend, Beena Nair

However, Nahshon Shannon's coworkers and boss said he never mentioned his daughter's disappearance.

Nahshon told investigators he spoke to Janessa on Facebook during the time she was missing. But deputies say those messages never existed.

What does exist? Records stored by Facebook that show Nahshon Shannon's GPS location the night Janessa went missing.

The report also describes evidence investigators gathered at the crime scene that deputies say leads back to Nahshon Shannon:

  • Tire marks in the woods where Janessa's body was found that investigators said were only a 1/16th difference from the car Nahshon Shannon drove;
  • Dirt recovered from Nahshon Shannon's car that they said was a 99.9 percent match to samples taken from the woods;
  • A shovel found in Nahshon Shannon's garage that investigators said had dirt on it and was missing two screws that were consistent with one located at Janessa's gravesite, according to the report.

Janessa's body was found in mid-July in a wooded area of the Triple Creek Nature Preserve.

Nahshon Shannon has a prior record of felony convictions, including felony battery, sexual assault and burglary, according to Hillsborough deputies.