Domingo, an infantryman who served a combat stint in Afghanistan in 2013, has been charged with providing material support to terrorists. Domingo is to appear Monday afternoon in court to face charges.
Investigators conducted an online sting operation, during which Domingo allegedly told an undercover Federal Bureau of Investigation source to find a bomb-maker and purchased several hundred nails to use as shrapnel.
"Domingo said he specifically bought three inch nails because they would be long enough to penetrate the human body and puncture internal organs", the compliant says.
Information from the Associated Press and ABC News was used in this report.
In one conversation described in court documents, the undercover Federal Bureau of Investigation agent warned Domingo that he would probably be caught by authorities if he went ahead with his plan.
When asked if he planned to get caught, he answered "Martyrdom, bro", according to NBC, quoting from the indictment.
On Friday, the undercover operative gave Domingo "multiple inert devices" that Domingo believed to be live bombs. The Army veteran, according to the affidavit, expected his terror plot to kill "at least" 20 people and injure 30 others.
Once the dummy bombs were delivered to Domingo Friday by two undercover operatives, Domingo then walked the area of the planned Long Beach rally with the operatives to determine the best place to plant the bombs "in order to inflict the maximum number of deaths".
Domingo posted online about violent jihad, praised ISIS and wanted to become a revenge martyr.
The documents also indicated that Domingo said he kept an AK-47 in his bed, in light of the attack.
Authorities said he was referring to the New Zealand mosques massacre the previous day in which 50 people were killed.
After considering various options - including targeting Jews, churches, and police officers - Domingo chose to detonate an IED at the Long Beach rally, which ended up not taking place, authorities said.
According to prosecutors, Domingo had declared his fidelity to Islam on March 2.
A terror plot by an American Army veteran who converted to Islam and planned to bomb a white supremacist rally in Southern California as retribution for the Christchurch mosque shootings was thwarted, United States federal prosecutors say.
Federal officials said Domingo had recently converted to Islam and experienced a "rapid radicalization to violence".