The plan was so detailed, right down to zip-ties "on the door handles so b-----s can't escape," that a very frightened Catherine O'Connor called the police on her own grandson.
"He's planning on having a mass shooting at one of the schools," she calmly told the 911 operator in Everett, Wash. Then there was the matter of the rifle she said she found inside a guitar case in her grandson's bedroom.
The 18-year old was arrested Wednesday at ACES High School and charged with attempted murder, assault, and armed robbery.
The latter two counts stemmed from Joshua Alexander O'Connor kicking an officer while trying to escape arrest, and the robbery of a convenience store earlier in the week to raise money for his planned terror attack, according to court documents.
The entries in his journal were methodical and written in point-by-point detail, police said. They were also chilling in the teen's excitement at the prospect of killing his fellow student a ACES.
"I can't wait," he wrote, according to court documents.
Officers found an AK-47 in the teenager's bedroom, along with grenades and materials for making pressure cooker bombs, according to search warrant affidavits filed in court.
"It's too f---ing easy to buy a gun," he wrote on Jan. 25, police said.
Under the heading of "Outline for Ace's massacre," the teen wrote:
"Bring gear and weapons (wait till lunch). Wait 2-3 minutes after lunch bell and go to gym backdoors by student parking, and put zip ties on door handles (so b----s can't escape). Set up pressure cooker bomb by bleachers with most students. Walk out of gym and zip tie gym doors by Tom's history class.
"As soon as FTP bomb goes off, start shooting spree and start music. Throw pipe bomb and and smoke bomb in office. Mow down kids in hallway and gym. Kill yourself at the end of Make a change."
Police said they weren't sure who "Tom" is or about the reference to "Make a change."
The journal entries mentioned April 19, police said. The Oklahoma City bombing occurred on April 19, 1995, and the day and month are considered significant in anti-government and white supremacist circles.
O'Connor made his first court appearance Wednesday, the same day Nikolas Cruz allegedly walked into his old high school and opened fire, killing 17.
The Washington teen has not entered a plea.