Originally Published: 02 JUN 22 10:03 ET

By Mark Morales, CNN

(CNN) -- The 18-year-old indicted in last month's racist supermarket shooting in Buffalo, New York, that left 10 people dead is scheduled to be arraigned Thursday afternoon, a spokesperson for the Erie County prosecutor said.

A grand jury Wednesday indicted Payton Gendron on 25 counts, a law enforcement official said.

The shooting suspect faces 10 counts of first-degree murder, 10 counts of second-degree murder as a hate crime and three counts of attempted murder as a hate crime, according to court documents. He also faces a domestic terror charge and a weapons charge, the documents show.

Authorities allege ample evidence indicates the White teen was motivated by race and that he targeted a supermarket in a predominantly Black community.

He is slated to be arraigned in Erie County District Court at 2 p.m. ET, said Kaitlyn Munro, spokesperson for the county district attorney's office.

The teen was placed on suicide watch after his arrest, Erie County Sheriff John Garcia said.

Official: 'No mistake' it's a hate crime

Eleven of the 13 victims at Tops Friendly Markets were Black and two were White, officials said. Among the victims, ranging in age from 20 to 86, were a heroic former police officer who tried to stop the gunman and a long-term substitute teacher and a taxi driver who, according to his nephew, "took pride in helping people."

More charges could come at the federal level, as authorities are investigating the shooting as both a hate crime and a case of racially motivated violent extremism, said Stephen Belongia, FBI special agent in charge of the Buffalo field office.

Gendron arrived at the market in the middle of the afternoon on May 14, "very heavily armed" and wearing tactical gear, Buffalo Police Commissioner Joseph Gramaglia said. He also had a camera and livestreamed his rampage, the commissioner said.

He allegedly opened fire in the store parking lot, shooting four people, before entering the store where he killed the former policeman, who was working as a security guard, Gramaglia said. Gendron then shot eight more people inside the store before surrendering to police, the commissioner alleged.

During his arrest, the suspect made disturbing statements describing his motive and state of mind, including an acknowledgment he was targeting the Black community, according to an official familiar with the investigation.

"The evidence that we have uncovered so far makes no mistake that this is an absolute racist hate crime," Gramaglia said. "This is someone who has hate in their heart, soul and mind."

Garcia described the shooting as "pure evil," adding that it was a "straight-up racially motivated hate crime."

Documents indicate premeditation

In a 180-page document purportedly written by the suspect and posted online before the shooting, the author describes himself as a fascist, White supremacist and anti-Semite and writes that White Americans are being "replaced" by people of other races.

The document, which CNN has obtained, also provides minute-by-minute details of the alleged deadly plan, including a color-coded map of the store and the equipment and clothing he planned to use -- from military-style body armor down to his brand of underwear. It also lays out how the author intends to "shoot all black people."

The suspect visited the store in March and again the day before the shooting to gather information about the location, officials said.

Further investigation revealed Gendron made a "generalized threat" while attending Susquehanna Valley Central High School last year, and state police visited him after he did a school project on murder-suicides, officials said.

"The state police arrived at his house at that point last year," Garcia said. "He stayed at a facility -- I'm not sure if it was a hospital or a mental health facility -- for a day and a half."

The suspect planned to continue his shooting rampage beyond the supermarket, Gramaglia said, adding there was documentation indicating he allegedly planned to target "another large superstore."

In social media posts, Gendron wrote that online research led him to target the 14208 zip code because it has a higher Black population than other locations he was considering.

He also says he pondered attacking a church or an elementary school but chose the supermarket because of how many people frequent grocery stores. He used Google's popular times feature for Tops Friendly Market in determining the busiest time of day to attack the store, the posts show.