William Atchison has been identified as the gunman in Thursday's shooting at a New Mexico High School.
Atchison, 21, worked at a local gas station and posed as a student to sneak into Aztec High School.
Casey J. Marquez, a senior, and Francisco "Paco" Fernandez, a junior, were killed in the shooting.
"This person is not only a coward, he is evil," San Juan County Sheriff Ken Christesen said. "In my mind there are so many things wrong with this."
New Mexico State Police Chief Pete Kassetas said authorities don't believe Marquez and Fernandez were targets, and that Atchison intended to kill many more students.
Atchison mingled with students before shooting Fernandez in a restroom and Marquez in a hallway, Kassetas said.
Atchison then walked the school's hallways firing bullets into classrooms before killing himself, Kassetas said.
Atchison had a thumb drive on him that detailed his plans for the school shooting and his suicide. "Work sucks, school sucks, life sucks. I just want out of this (expletive)," the note read.
Christesen said Atchison lived with his parents and had no criminal record, but the FBI said they had previous contact with Atchison over concerning posts on an online gaming forum.
The shooter is among the three people dead after a shooting at a New Mexico high school, according to New Mexico State Police.
The two others killed in the shooting were students at Aztec High School. Police did not release details about the shooter.
Three people are dead following a shooting Thursday at a New Mexico high school, authorities said.
The deceased are believed to be students at Aztec High School, San Juan County Sheriff Ken Christesen said.
Christesen said the shooter is dead, but he did not say if the shooter was counted among the three casualties.
Authorities said all buildings at the school had been cleared and students had been bused to another location to be reunited with their parents.
The school is located in the Four Corners region, near the Navajo Nation.
Federal agents and state police are investigating the shooting.
The Associated Press contributed to this report.