Suspected in a mass shooting at a Tops store in Buffalo, New York planned attack at least two months, according to new documents.

An 18-year-old man from Canclin, New York, is charged with first-degree murder, 10 people were killed and three were injured. The mass shooting is being investigated as a hate crime.

The 589-page document states that the suspect visited the Tops store on March 8, more than two months before the attack, and collided with a security guard. The document describes his interaction with a black armed store guard.

One of the victims of Saturday’s shooting was Aaron Salter, a Tops guard. Salter shot at the suspect but did not pierce his body armor. The suspect opened fire in response and killed Salter. It is unclear whether Salter was the same security guard who confronted the suspect in March.

The document includes sketches of peaks with delineated passages. It also includes posts on social media dated December 2021. Messages were made on Discord, a platform where users can communicate in private and public services using voice, video and text. They can also upload files and media.

According to ABC News, investigators are finding out the origin and authenticity of the document and trying to determine who else could have access to it.

The suspect is in Erie County without bail. The criminal case is scheduled for May 19.

This story was originally published August Erbacher of WKBW in Buffalo, New York.