TONKAWA, Oklahoma - A 13-year-old girl is in a juvenile detention center after she is accused of plotting to shoot and kill former classmates, Tonkawa police said.

Police said they found weapons and a diary in her home detailing what she planned to do.

Tonkawa Public Schools Superintendent Lori Simpson said the investigation started Sunday morning, after a local parent called police about a threatening text message sent from the girl.  

Police said a search warrant was issued for the girl's home and they found firearms, weapons, ammunition and a manifesto written by the girl.  

Police said the girl planned to shoot and killed former classmates at Tonkawa High School, where the girl used to attend.

“You hear it all over the country, if you see something say something, and that’s exactly what happened here,” said Tonkawa police Corporal Nick Payne, who is heading up the investigation.  

Payne said police are investigating whether or not the girl had been a victim of bullying at the school. He said she recently was being homeschooled.  

“This is full-blown, grown-up stuff,” he said. “The fact a 13-year-old girl was contemplating this is detrimental enough.”