The student posted the threat on Instagram on March 15 and targeted students at Molina High School.
Jose Gonzalez, 17, has been identified as the suspect. The post talked about killing gay students and shooting up the school. He also detailed how he would place explosives at the school's graduation ceremony.
Three students came forward after seeing the threats online, and Dallas ISD police credited them for having the courage to say something to authorities.
Gonzalez was charged with making a terroristic threat and jailed on $2,500 bond. He made bail and currently is out of jail.
FOX4 was told Gonzalez, a senior, was in the top 10 percent of his class and enrolled in three AP classes.
Dallas ISD investigators determined that at the time he allegedly posted the threat, Gonzalez had been listening to death metal music.
"While listening to this music that contains some very graphic images, he elected to send out an email via Instagram…that talked about IEDs, that talked about harming people at the school and things he wanted to do at the school," said Dallas ISD Police Chief Craig Miller.
When one of Gonzalez's friends confronted him about it, school police say he replied that he was absolutely serious.
Gonzalez was pulled out of class Friday.
"As we were leaving, a cop took a student with him and we weren't really sure what happened," said Molina High junior Desiree Leija.
Most students didn't learn of the threats or subsequent arrest until Monday, when letters went home to parents.
Molina parents said they're relieved that school police reacted so quickly.