The 17-year-old Tennessee boy who allegedly killed a classmate at his high school on Wednesday was possibly corresponding online with a 15-year-old girl who killed a student and teacher in Wisconsin last month.

A source told ABC News that Solomon Henderson left behind a 51-page document in which he expressed self-hatred about his race and hoped for violence against other Black people and Jews. Sources also claimed that Henderson’s social media suggests he was in contact with Natalie Rupnow, who killed a teacher and student at Abundant Life Christian School in Madison, Wisconsin, before also taking her own life.

READ: Student Shooter ID’d in High School Shooting That Left Girl Dead

According to the sources, Rupnow was following Henderson on an undisclosed social media platform. ABC reported that authorities are investigating whether a BlueSky account belongs to Henderson. The account posted an edited picture of Rupnow a day before Henderson allegedly opened fire at Antioch High School in Wisconsin, killing Josselin Escalante, 16, and wounding another student. Henderson then killed himself in the school’s cafeteria, where the shooting transpired.

Metro Nashville Public Schools spokesperson Sean Braisted confirmed to ABC that an AI gun-detection system — called Omnilert — failed to detect the gun at the high school before Wednesday’s shooting. He said the program went off after armed guards entered the high school.

“These systems can only detect weapons the cameras can see,” he said. “In this case, the system didn’t work because of where the shooter was and the position of the gun.”

[Feature Photo: Metro Nashville Police/Facebook]