A Washington state mom turned her 17-year-old son in to police upon finding plans in his journal to carry out a school shooting on the anniversary of the Columbine High School massacre.

“It’s devastating. I know I did all I can do and that I made the right choice,” the mother, who only identified herself as Nicole, told CBS News about the decision that led to her son’s Sept. 17 arrest on harassment and bomb threat charges.

The teen, in his journal, said he’d use guns and a variety of explosives to carry out the attack on College Place High School, according to police records obtained by KTEL News.

With the weapons, he’d “blast anyone in sight” and “kill everyone possible,” some of his notebook entries read, the outlet reported.

The teen made a note to “kill self after maximum damage” in the writings.

His mother said he told her that he was just being imaginative. The entries were “just a story,” Nicole said was his response.

But Troy Tomaras, College Place police chief, wasn’t buying it.

“Well, he’s plotting to attack and kill people,” Tomaras told CBS News.

“That’s beyond creative writing. That’s beyond normal.”

Tomaras commended Nicole for speaking up.

“She’s very courageous,” he said. “It’s clearly very emotional for her. She loves her son.”