'Sovereign Citizen' Allegedly Launches Full-Blown Assault on Atlanta Courthouse

Police investigate the home of a man who attempted to blow up a public building in Georgia.
4:13 | 06/07/14

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Transcript for 'Sovereign Citizen' Allegedly Launches Full-Blown Assault on Atlanta Courthouse
This morning, police are investigating the home of a man with anti-government views who allegedly launched a full-frontal, heavily-armed assault on a courthouse in Georgia. The video was frightening. And this morning, a deputy is being hailed as a hero for stopping the gunman before he carried out his twisted plot. ABC's Steve osunsami has the latest. Reporter: Good morning. The police say this could have been a slaughter. That's the word they're using this morning. And they're crediting that deputy with saving many, many lives. Witnesses recording it on their cell phones couldn't believe it. Listen for yourself. That's gunfire. A gunman in a silver SUV, trying to drive through the front of the Forsyth county courthouse north of Atlanta. I heard pat, pat, pat. Maybe three or four. Reporter: Look here. Authorities say that Orange smoke is smoke from grenades he dropped to stop police. They say the gunman was Dennis Marx, a self-described sovereign citizen who hated the government and was due in court Friday to answer drugs and weapons charges. Police say he shot deputy Daniel rush who was working outside. And the deputy shot back, a decision that saved everyone in the busy courthouse. The officer that was shot as a fractured fibula and tibia in his right leg. The deputy saved several lives. Reporter: Police say Marx was carrying an assault rifle, tear gas, hand grenades, a bomb and flex ties he planned to use to restrain people. They found four explosive devices at his home. A whole team of deputies at the courthouse rushed to the scene of the shooting and opened fire. Marx was killed in the gun fight. They shot windows out of the car. And the guy fell out on the crown. Reporter: Marx's hearing was over an alleged marijuana possession with intention to distribute. Last year, he filed a lawsuit against the sheriff's department, accusing deputies of illegal searches and using excessive force. The family of the injured deputy say they have received threats on social media from Marx's supporters. Police have dealt with Marx before. Saying he's a known problem. They continue to investigate his home. Dan and bianna? Thanks. This is not the first time a so-called sovereign citizen has turned violent. The FBI has dedicated sovereigns as domestic terrorists. I've covered this movement for many years. Take a look. I'm a sovereign. I'm not a American citizen. Reporter: They have disrupted courtrooms. The unit has shots fired. Reporter: Led police on high-speed chases. And even engaged in murderous shoot-outs with police. As you can see this video of a 16-year-old emerging from his father's van with a rifle and killing two officers. There are an estimated 300,000 sovereign citizens in America. It's a decentralized leaderless movement, loosely built around an ideology, which argues that people who declare themselves sovereign, don't have to follow the laws the rest of us do. So, many sovereigns believe they don't have to get driver's licenses, pay taxes or honor their debts. Sovereigns have even attempted to take possession of foreclosed homes. As this 23-year-old rapper did in a neighborhood of boca raton, Florida. That young man was linked to this figure, James Mcbride, the founder of a mysterious group called divine province. He gives classes around the country and claims that his power derives from this seal, which was a gift from former pope Benedict. Are you saying you have some sort of papal authority here in north America? In the globe. Reporter: In the globe? That's right. Reporter: So, you have primary control of the Earth? Correct. Reporter: That seems like a lot of power. I understand. It is. And a lot of responsibility. Interesting conversation there. We should say that most sovereigns, including that man, James Mcbride, vocally disavow violence. But sometimes, sometimes, when their beliefs repeatedly over and over clash with the government some can lash out. And it's frightening to think it could have been worse, if it were not for that police officer they're calling a hero this morning. We're going to go to the

This transcript has been automatically generated and may not be 100% accurate.

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