Dennis Mahon, a longtime leader in the national White supremacy movement, and his brother have been arrested by federal agents in connection with the 2004 letter bombing of Don Logan, who is Black and at the time headed Scottsdale's diversity office.

A federal grand jury indicted Mahon and his twin, Daniel Mahon, June 16 on charges of conspiracy to damage buildings and property by means of explosive. Dennis Mahon was also charged with malicious damage of a building by means of explosives and distribution of information related to explosives.

The arrests cap a lengthy investigation that languished until last year, when federal officials revealed that new DNA bomb technology had revealed at least one suspect in the letter bombing, which also injured two other city workers.

Logan issued a written statement Thursday saying the arrests were welcome news.

"Although very excited about the arrest, we're cognizant of the fact that this is the first step in the judicial process," he said.

Logan has recovered from his severe injuries and now directs Glendale's diversity programs.

The indictment alleges that the Mahon brothers taught others how to make a package pipe bomb using a 9-volt battery, among other components. It also alleges that they mailed books explaining the manufacture and use of improvised explosive devices.

Both were arrested Thursday outside Rockford, Ill.

Also charged in connection with the bombing was Robert Neil Joos of Missouri. After a search of his 200-acre property, Joos, 56, was charged Thursday in U.S. District Court in Missouri with being a felon in possession of firearms.

Joos' arrest stems from the Logan bombing investigation. An undercover agent told authorities that Mahon described Joos as a "longtime white supremacist associate and an expert on weapons, explosives, bomb making and general survival skills," according to court documents.

Authorities were scheduled to hold a briefing today in Phoenix to discuss the arrests and indictments.

Dennis Mahon is an outspoken racist who has long been cited by national organizations that monitor hate groups as a leader in the White separatist movement in the U.S. According to the Anti-Defamation League, the Mahon brothers have been active in White supremacist groups in several states in the Midwest and in Arizona since the 1980s.

Published reports say Dennis Mahon was once deported from Canada for his activities and that he has reached as far afield as Germany to recruit new members for the Ku Klux Klan. The White Aryan Resistance, in which he has long had a leadership position, believes in a separate homeland for Whites.

After the 1995 bombing of the Alfred P. Murrah Federal Building in Oklahoma City, which killed 168 people, Dennis Mahon boasted of knowing Timothy McVeigh, who was convicted in that bombing. Although McVeigh was executed in 2001 for his role, Dennis Mahon defended him and vowed to espouse his cause.

During McVeigh's trial, defense attorneys suggested Dennis Mahon and others linked to an Oklahoma White supremacist compound had discussed blowing up federal buildings.

Conspiracy theorists since have sought to tie Mahon to the Oklahoma City bombing.

In 2001, Dennis Mahon tried to move his base of operations to Arizona, organizing racist allies in Gilbert and Kingman. Though he met resistance from local religious and anti-hate groups, he continued operating in Arizona off and on and was in the state shortly before the bombing that injured Logan.

According to the indictment, Dennis Mahon called Scottsdale's Office of Diversity and Dialogue on Sept. 26, 2003, and left a voice message saying that "the White Aryan Resistance is growing in Scottsdale. There's a few white people who are standing up."

According to the ADL, Dennis Mahon was also in Phoenix in February 2004 to attend Aryan Fest.

Aryan Fest is a White- power music festival and gathering in Phoenix that was sponsored by Volksfront, a neo-Nazi group. The event attracted members of the Ku Klux Klan, neo-Nazi skinheads and representatives from other extremist groups.

During conversations at Aryan Fest, Mahon reportedly promoted violent, terrorist activity, specifically "nuk[ing] D.C." According to a news account of the event posted on ADL's Web site, Mahon stated, "You nuke D.C., you're going to wipe out most of the politicians, plus a couple million crack-head n-ggers. . . . It's a win-win. . . . And I think it's the only way, I really do. Terrorism works. We did a lot of terrorism in Tulsa in the 1980s. We put heads in the road, and people paid attention."

During that same period, the indictment alleges, Dennis Mahon helped construct a bomb, disguised in a cardboard box made to appear as a parcel package that was delivered to Scottsdale's Civic Center Library on Feb. 21, 2004. It was addressed: Don Logan, Office of Diversity & Dialogue.

When Logan opened the box on Feb. 26, 2004, it exploded in his hands.

Two women were injured in the blast, but their injuries were minor. Logan, however, was badly injured and later underwent surgery to repair his hands and arms.

For the most part, security measures Scottsdale put in place after the bombing remain, said Sgt. Mark Clark, a spokesman with the Scottsdale Police Department.

"It's been five years of the investigation, and we're very happy that it's come to the point that the federal investigators have been able to make an arrest," Clark said.