A Reseda man was behind bars Monday on suspicion of plotting to carrying out a domestic terrorism bombing during a white-nationalist rally in Long Beach that never materialized.

Mark Steven Domingo, 26, of Reseda, a former U.S. Army infantryman who served in Afghanistan, was arrested Friday after he received what he thought was a bomb, but was actually an inert device supplied to him by an undercover law enforcement officer, federal officials said.

At a Monday news conference, the FBI said Domingo was arrested Friday after he finalized his plans. He reportedly bought several hundred three-inch nails to use as shrapnel in bombs long enough to puncture internal organs.

He said "there must be retribution," following mosque attacks in New Zealand, according federal officials.

Federal authorities said Domingo considered a variety of targets -- including police officers, churches and a military facility -- but ultimately planned to set off an explosive device during what was anticipated to be a white nationalist rally at a Long Beach park on Sunday.

There was no ongoing threat or co-conspirators, federal officials said.

City News Service contributed to this report.