(CNN) A 27-year-old man who allegedly espoused white supremacist ideology online was arrested by the FBI and accused of plotting to bomb a synagogue in Colorado.

Richard Holzer had brought a knife and a mask to a motel room and was examining inert pipe bombs prepared by undercover agents moments before he was arrested late Friday, according to a criminal complaint.

Holzer is charged with attempting to obstruct the free exercise of religious beliefs with the attempted use of explosives -- a hate crime. In court documents, officials called him a domestic terrorist and described his alleged anti-Semitic ideology and desires for a racial holy war.

According to the complaint, Holzer talked about killing Jews in forums online and shared video of himself casing a synagogue in Pueblo. He described himself as a skinhead, and shared pictures of himself with other social media users with guns and knives alongside white supremacist symbols, the complaint says.

Holzer, according to prosecutors, wrote on one Facebook account: "I wish the Holocaust really did happen .... they need to die."

Temple Emanuel in Pueblo, Colorado, was allegedly the object of a bomb plot.

He also said he paid a "witch doctor" $70 to put arsenic in the water pipes of the synagogue and "hex" the place last year, according to the complaint.

Holzer made his first appearance in Denver federal court on Monday afternoon. A preliminary hearing and a detention hearing are scheduled for Thursday morning, according to US Attorney Jason R. Dunn.

The suspect, who does not yet have an attorney listed on his case, faces a maximum 20-year sentence if convicted of a hate crime, officials said.

How suspect came to FBI's attention

Domestic terrorism and hate crimes have become a growing concern for law enforcement in recent years as a number of high-profile attacks have left scores dead across the country. Eleven worshippers were killed in October last year when a white supremacist opened fire at the Tree of Life synagogue in Pittsburgh.

Holzer first came on the FBI's radar after a tip in late September regarding comments he'd made online "of concern indicating a possible threat to the community," FBI Denver Special Agent in Charge Dean Phillips said at a news conference.

"This case emphasizes our continued efforts to aggressively and promptly address threats to our community to include violence against places of worship. I cannot stress enough the importance of reporting threats in our neighborhoods," Phillips said.

Undercover FBI agents approached Holzer online soon after the tip and were interacting with him as he allegedly plotted the attack on Temple Emanuel. In a meeting with three undercover agents at a restaurant in Colorado Springs last month, Holzer proposed using Molotov cocktails to destroy the Pueblo synagogue, according to the complaint.

"I want something that tells them they are not welcome in this town," Holzer allegedly said. "Let's get that place off the map."

Temple Emanuel Congregation President Michael Atlas-Acuña told CNN the small Jewish community of about 35 families hasn't had any similar threats in the past.

"The Pueblo community has embraced the Jewish community and we've never had any kind of threats or vandalism or anything like this," Atlas-Acuña said. Holzer, he said, is a "transplant" and not from Pueblo.

The synagogue has had security guards, though, for the past few years, after shootings in other places, he said, and a sign in front states it isn't a gun-free zone, Atlas-Acuña said.

"I think it's stupid for people to put signs up that say this is gun-free zone," he said. "Like advertising. They're hitting soft targets and churches, and synagogues are soft targets."

The temple is 119 years old and on the National Register of Historic Places, Atlas-Acuña said. It's never been closed for any reason, and services will be held as usual after this week's threat.

Authorities say they have video evidence

Holzer allegedly visited Temple Emanuel multiple times after he hatched his plot with the undercover agents. On October 19, Holzer sent one agent a video of himself walking around the exterior of the synagogue and "commenting on various features of the building," the complaint says.

On the night of November 1, Holzer donned a Nazi armband and drove with an undercover agent to a motel. There, he toasted a "move for our race" and commented that the pipe bombs, which authorities said had been prepared with simulated black powder at the FBI lab in Quantico, Virginia, looked "absolutely gorgeous," according to the complaint.

The FBI arrested him soon afterward and took him to a local police station, where he admitted to planning to blow up the synagogue, the complaint says.