SAN FRANCISCO (KPIX 5) — A militia group known for being heavily armed has confirmed it’s coming to San Francisco.

The group of ex-military and law enforcement officers claim to keep the peace at potentially violent events.

They’re known as the Oath Keepers, a national group whose members often show up to rallies packing heat.

They’re adding a whole new element to the debate over an upcoming Patriot Prayer rally.

Oath Keepers founder Steward Rhodes spoke at a protest in Boston in May, saying, “You know we’re all in this together but a lot of radical left have abandoned the Constitution and have openly declared they are going to use force and violence against those they disagree with.”

They’re often heavily armed, like we saw when they showed up in Ferguson, Missouri in 2015.

On Friday, we learned they plan to attend a Patriot Prayer event at Crissy Field on Saturday, August 26.

San Francisco Mayor Ed Lee has sounded the alarm. “This oath group is known to carry arms in a very public way. Obviously, that instills in us yet again the need to reevaluate this particular rally because it is more threatening than we have ever saw,” Lee said.

The National Park Service granted the permit at Crissy Field.

Police Chief Bill Scott confirmed that while openly carried weapons are not permitted, concealed weapons are allowed at Crissy Field if a person has the proper permit.

Scott said, “The laws of the state does permit concealed weapons with the proper approval and we have to abide by the laws of the state. On federal property those same laws are applicable.”

He pointed out that the National Parks Service could restrict guns and other items from the event.

When we talked to the founder of Patriot Prayer, Joey Gibson, he said his group is peaceful. But he did say some supporters may bring weapons.

“I would assume that if there is a lot of, probably a lot of people, if they can legally carry I’m sure they would – that’s what a lot of Americans do,” Gibson said.

Professor Brian Levin with the Center for the Study of Hate and Extremism at California State University, San Bernardino said, “We’re seeing an escalating arms race now, where people across the country from both sides are showing up not just with baseball bats and sticks but with guns.”

He says the Oath Keepers can diffuse certain situations, but sometimes they make things worse.

“The bottom line is sometimes, believe it or not, these people can be good at herding their members away from confrontation,” said Levin. “But when you have private militias who aren’t answerable to anyone showing up with long rifles at extremely volatile, incendiary events the risk of violence is not decreased, it’s increased.”