Local and federal law enforcement officials thwarted a man's terror plot to detonate improvised explosive devices at several Southern California locations to cause "mass casualties," authorities said Monday.

Mark Stevens Domingo, 26, an Army veteran, was arrested Friday night after he took delivery of what he thought was a live bomb from an undercover law enforcement officer posing as a bomb maker, authorities said. He was charged with attempting to provide material support to terrorists, reports the Los Angeles Times.

According to a federal affidavit, "after considering various attacks – including targeting Jews, churches, and police officers – Domingo decided to detonate an IED at a rally scheduled to take place in Long Beach this past weekend. As part of the plot, Domingo asked his confederate – who actually was cooperating with the FBI as part of the investigation – to find a bomb-maker, and Domingo last week purchased several hundred nails to be used as shrapnel inside the IED."

Prosecutors alleged Domingo sought retribution for the New Zealand mosque attack and said he was willing to become a martyr. "There must be retribution," he said in an online post, according to the federal criminal complaint. He also allegedly expressed allegiance to Islamic State.

"America needs another vegas event …[to] give them a taste of the terror they gladly spread all over the world," he allegedly wrote in reference to the massacre at the Route 91 concert.

The FBI saw the posts and used an informant to begin a series of meetings with him.

A domestic terror plot aimed at "multiple targets" in Southern California was disrupted by federal and local law enforcement agencies, sources told the Los Angeles Times on Monday.

One man, described as a U.S. military veteran, was caught in an online sting operation and arrested by the FBI, according to law enforcement officials who spoke on condition of anonymity because they were not authorized to discuss the case with the media.

It’s unclear how far the plot got, but sources said the man had specific targets, including one in Long Beach. The sources said he had converted to Islam, but it was not known if that was related to the plot.

"It sounds like he tried to connect with other like-minded folks online," one source said.

An official who said the plot involved “multiple targets” declined to elaborate further.