The gunman who killed New Mexico high school students before allegedly turning the gun on himself posted his sinister plans on the Internet before his killing rampage.

On Thursday, 21-year-old William Atchison disguised himself as a student and walked into Aztec High School at 8 a.m. with a .9mm Glock and multiple magazines in a backpack, according to San Juan County Sheriff, Ken Christesen.

Atchison, a former student at Aztec, shot two students as he roamed the halls of the school, Fox News reports. The students were identified as Casey Marquez and Francisco Fernandez, who had both been in the hall at the time. Police believe they were not specifically targeted but in the wrong place at the wrong time.

The gunman continued to fire into classrooms at random. A janitor shouted to teachers to quickly lock their classrooms to protect the students. A substitute teacher in a computer lab couldn’t lock the classroom door, so she hid students in an office and barricaded the door. Atchison allegedly walked into the classroom, firing shots and yelling that he knew they were in there.

Christesen said the teachers’ actions saved a lot of students.

“Their swift action saved a whole lot of lives and a lot of devastation.”

It’s believed that Atchison committed suicide in the school.

Police said he posted a threat to social media the morning of the killings, detailing his plans, according to New York Daily News.

“If thing go according to plan, today would be when I die. I wait until the school buses are detected, then head on foot disguised as a student. I go somewhere and gear up, then hold a class hostage and go ape-s—, then blow my brains out.”

As for motive, he only said that, “work sucks, school sucks, life sucks. I want out of this s—.”

GoFundMe pages have been created to help the families of Casey and Francisco.

[Feature Image: Casey Marquez and Francisco Fernandez/GoFundMe]