The Department of Homeland Security on Thursday announced that Abraham Hermosillo Alvarez, a 31-year-old Mexican national living in Omaha, Nebraska, was the alleged mastermind behind a foiled terrorist plot targeting the UFC Freedom 250 event held at the White House last weekend.

Federal authorities arrested Alvarez on June 14 during a raid at an abandoned church in Western, Nebraska.

According to court filings and Justice Department allegations, Alvarez, who allegedly used the alias "Shepherd" in encrypted communications, coordinated and directed a multistate conspiracy to carry out a mass-casualty attack against government officials and other attendees at the event.

The Justice Department charged Alvarez and four co-conspirators arrested in Ohio, Missouri, and California with conspiracy to commit murder and conspiracy to commit violence on White House grounds.

Prosecutors allege the group planned to use explosive-laden drones to trigger an evacuation before deploying snipers against "high-value targets" fleeing the venue.

Investigators say Alvarez organized the plot through encrypted group chats, where he allegedly discussed obtaining drones and explosives and encouraged participants to make the attack "as deadly as we can get."

The FBI also alleges he identified sniper positions, drone launch sites, and escape routes.

DHS said Alvarez entered the United States on a B-2 visitor visa and remained after it expired in December 2001.

The department said he later received Deferred Action for Childhood Arrivals (DACA) status in 2014. Immigration and Customs Enforcement has lodged a detainer against him.

"This illegal alien from Mexico should never have been allowed in our country," DHS acting Assistant Secretary Lauren Bis said in a statement, adding that Alvarez and his alleged co-conspirators "will face justice."

The FBI said the investigation began after authorities became aware of a potential threat on June 10.

Officials credited a multistate operation involving the FBI, Department of Justice, Secret Service, and other law enforcement agencies with disrupting the alleged plot before it could be carried out.

All five defendants are presumed innocent unless proven guilty in court. If convicted of conspiracy to commit murder, they face potential sentences of up to life in prison.