The transgender student accused of shooting up a Colorado school told police that he wanted other students to “suffer from trauma like he had to in his life.”

One of the two alleged shooters, 16-year-old Alec McKinney, is transgender and identifies as male. McKinney told officers that he wanted to take revenge on students at the STEM school in Colorado for how they treated him.

McKinney allegedly carried out the May 7 shooting at the STEM School Highlands Ranch in Highlands Ranch, Colorado alongside 18-year-old Devon Erickson. The shooting left one student dead and eight others wounded.

McKinney told investigators that classmates “hated him” and called him “disgusting” for trying to transition from a female to a male. McKinney said that he planned to specifically target those who made fun of him, according to police documents. McKinney also said that he has had suicidal and homicidal thoughts since the age of 12.

The documents, unsealed Thursday, reveal that the two exchanged messages over social media the night before the shooting. In the messages, McKinney allegedly told Erickson that he was “super suicidal” and was considering killing his mom and siblings. Erickson also told investigators that both he and McKinney used cocaine prior to the shooting.

McKinney and Erickson were arrested after some of the students fought back the alleged shooters. The student who died, Kendrick Castillo, was killed while charging the shooter and has been hailed as a hero.