The FBI arrested a self-proclaimed white supremacist who allegedly planned to blow up a historic Colorado synagogue and poison congregants as part of a “racial holy war,” federal officials said Monday. Investigators called the alleged plot a hate crime and an act of domestic terrorism.

Richard Holzer, 27, was arrested Friday night after picking up what he thought was a bundle of pipe bombs and dynamite from undercover agents, according to an affidavit filed in federal court in Denver. He was wearing a Nazi armband during the meeting and carrying a copy of “Mein Kampf,” FBI Special Agent John W. Smith wrote in the filing.

Investigators said Holzer wanted to blow up the Temple Emanuel synagogue in Pueblo, Colo. The structure is the state’s second-oldest synagogue and is listed on the National Register of Historic Places.

Holzer was arraigned Monday afternoon on a charge of attempting to obstruct people from exercising their religion through force and attempted use of explosives and fire. He faces up to 20 years in prison if convicted. The public defender assigned to represent Holzer did not immediately respond to a request for comment Monday, and it was not immediately clear if he had entered a plea.

“We thwarted an imminent threat to our community,” FBI Special Agent in Charge Dean Phillips said in a news conference.

Holzer’s arrest comes as Jewish institutions around the country are still reeling from the mass shooting last October at Pittsburgh’s Tree of Life synagogue. The alleged gunman left a trail anti-Semitic posts on social media before he fatally shot 11 congregants and wounded six others in the deadliest attack on Jews in U.S. history.

Following the massacre, Jewish groups and law enforcement officials gathered in Washington earlier this year to draw up plans for how they would respond to future attacks on Jewish facilities. Weeks later, on April 27, another gunman who allegedly posted anti-Semitic screeds online opened fire in a synagogue near San Diego, killing one person and injuring three others.

In addition to Holzer, at least 12 other people have been arrested in connection with plots or attacks against Jews since the mass shooting at the Tree of Life, according to the Anti-Defamation League, which says the arrests reflect a recent spike in anti-Semitic incidents in the United States.

In 2017, incidents targeting Jews and Jewish institutions surged 57 percent, the ADL reported, attributing the jump to an increase of reports in high schools and on college campuses. Anti-Semitic incidents dipped slightly last year, the ADL said, but 2018 still represented the third-highest year on record for anti-Semitic violence and harassment since the group started collecting the data in 1979. In the first half of 2019, the ADL recorded 780 anti-Semitic episodes, on par with 2018.

Holzer first came onto the FBI’s radar earlier this year when investigators noticed a string of hate-filled, anti-Semitic posts on social media, according to the affidavit.

An undercover agent posing as a white supremacist reached out to Holzer on Facebook in late September, investigators said. After sending the agent pictures of himself holding guns and wearing swastikas and other white supremacist paraphernalia, Holzer bragged that he had tried to “hex and poison” the water at the Temple Emanuel synagogue in 2018, according to the affidavit. Investigators said he told the agent that he paid a cook to put arsenic in the water pipes and that he intended to do it again on Halloween.

His goal, he said, was to “make them know they’re not wanted here," according to the affidavit. He also allegedly told the undercover agent he was “getting ready for RAHOWA,” an acronym for “racial holy war” often used in white supremacist circles.

According to the affidavit, Holzer used several Facebook accounts to promote white supremacy and racist violence in direct messages and group chats.

“I wish the Holocaust really did happen,” he allegedly said in one message. “They need to die.”

He also allegedly sent pictures of himself posing with handguns and semiautomatic rifles while dressed in clothing featuring what FBI agents described as “white supremacy symbols.”

In other messages, he said he hated Jews “with a passion” and spoke about how he wanted to “die in a cop Shoot out,” according to the FBI. He allegedly told the undercover agent he was a former member of the Ku Klux Klan and a skinhead.

In mid-October, investigators said, Holzer and a friend met with multiple undercover agents at a restaurant in Colorado Springs, Colo., where Holzer talked about how he wanted to destroy the synagogue. When one undercover agent asked how he would do it, Holzer allegedly said he was considering Molotov cocktails.

The group then drove to the synagogue and discussed the possibility of using pipe bombs to inflict more damage, according to the affidavit. The undercover agents offered to supply the bombs, and over the following days they exchanged messages about how to go about the attack, investigators said. During that time, Holzer allegedly passed along videos of himself inspecting the building.

On Friday, Holzer rode with an undercover agent to a motel to meet two other agents, who presented him with two pipe bombs and 14 sticks of dynamite, all of which were inert, according to the affidavit. “This is absolutely gorgeous,” he allegedly said. He told the agents he wanted to detonate the explosives later that night, investigators said.

After his arrest, Holzer confessed to the plot, which he referred to as “my mountain,” according to the affidavit.

The Temple Emanuel, a Reform Jewish synagogue, opened in 1900. A representative from the synagogue did not immediately respond to a request for comment.

Pueblo Police Chief Troy Davenport called the alleged plot “intolerable in our city.”

“Mr. Holzer will now have the opportunity to explain his behavior through our court system in a constitutional way," Davenport said, “which, in the spirit of irony, protects religious freedom as one of its most golden rules.”