A federal grand jury has indicted an alleged white supremacist in connection with what prosecutors say was a plot to bomb one of Colorado's oldest synagogue, the U.S. attorney’s office said Friday.

Richard Holzer, 27, of Pueblo, was charged in early November with the attempted use of explosives and trying to obstruct the free exercise of religious beliefs, related to an alleged plot to attack Temple Emanuel, according to court records.

The grand jury added two other charges: attempted arson and using an explosive device to commit a felony offense, the U.S. Attorney’s Office in Colorado said in a statement.

If convicted, Holzer faces up to 50 years in prison, federal prosecutors said.

Holzer was arrested after undercover federal agents supplied him with pipe bombs and dynamite, which were inert and incapable of exploding, that he allegedly planned on detonating at the temple, according to the indictment.

A federal public defender who represents Holzer said he could not comment on a pending case.

Holzer allegedly used social media accounts to “promote white supremacy ideology and acts of violence, including racially- and religiously-motivated acts of violence” and “repeatedly expressed his hatred of Jewish people” and began planning the attack in September and October, according to the indictment.

Richard Holzer. El Paso County Sheriff's Office

Holzer allegedly said In a Sept. 3 Facebook message, "I wish the Holocaust really did happen…they need to die." An FBI agent posing as a white woman supportive of white supremacy contacted Holzer later that month.

Holzer sent the person pictures of swastika buttons and said he used to be in the Ku Klux Klan but was now a skinhead. He also sent photos of himself with firearms and said, "I'm getting ready for RAHOWA," which means a racial holy war, according to court documents filed in the case.

Holzer allegedly told FBI undercover agents he wanted to "vandalize the place beyond repair" and thought about using Molotov cocktails, but when he and the agents visited the temple, Holzer determined they wouldn't be powerful enough and settled on pipe bombs.

Holzer was arrested on Nov. 1, the same day he was given the pipe bombs and dynamite bundles by undercover agents. He had allegedly planned to carry out the attack that night.

Temple president Michael Atlas-Acuna walks past a memorial inside the historic Temple Emanuel in Pueblo, Colo., for the victims of the 2018 Aytz Chaim Synagogue shooting in Pittsburg, Pa., Tuesday, Nov. 5, 2019. Christian Murdock / The Gazette via AP

In an unrelated case in Northern California, an Oakland man who identified himself on gaming forums as a neo-Nazi and who discussed mass shootings of synagogues was charged with a federal count of lying to the Army about mental health treatment in order to enlist, prosecutors said Friday.

Ross Anthony Farca, 23, of Concord, was arrested in June by local law enforcement on charges related to statements he allegedly made in a chatroom of the online gaming service Steam. He allegedly talked about killing Jewish people, and authorities said they found an AR-15-style rifle, large-capacity ammunition magazines and books about Nazi life at his home.

He was charged by the state with making criminal threats and an unlawful assault weapon and possessing an assault weapon.

In the federal case, prosecutors say Farca claimed in 2017 that he had not received mental health treatment. But, they said, he had been seeing a psychiatrist since 2011 and was prescribed medication to manage his mental health, prosecutors said.

Farca reported to basic training on Aug. 28, 2017 and was discharged less than two months later after allegedly assaulting a fellow trainee. He was admitted to a psychiatric unit for 12 days, according to court documents unsealed Friday.

It was unclear Friday night if he had an attorney who could speak on his behalf.

His attorney in the state case, Joseph Tully, told The Mercury News in August that Farca is not a potential mass killer, and he suffers from a developmental disorder that prevents him from understanding why people took his remarks seriously.