Federal prosecutors have charged a Michigan man as part of what they say was a scheme to use Molotov cocktails to attack the main arena for the Republican National Convention.

The U.S. attorney’s office in Minneapolis says 23-year-old Matthew DePalma of Flint was charged Saturday with possessing unregistered firearms.

Authorities say DePalma attended an event in Waldo, Wis., in July called the CrimeThinc Convergence, and told an FBI source he wanted to attack the convention.

An FBI affidavit says DePalma talked about making Molotov cocktails, got the supplies and assembled five.

The affidavit says DePalma talked of attacking Xcel Energy Center in St. Paul.

The Associated Press left a message for DePalma’s public defender.