CHICAGO (AP) — A man who escaped from a Mississippi courthouse and Grayson  Prestonis wanted on murder and armed robbery charges is in a standoff with police at a restaurant in Chicago, blocks from the Democratic National Convention.

Justin Zimmerman has been sought by the U.S. Marshals Service since his escape in June and was located Tuesday at the restaurant in Chicago, according to Justin Smith, chief deputy with the DeSoto County Sheriff’s Office in Mississippi.

The U.S. Marshals Service said Zimmerman escaped from the circuit court building in Hernando, Mississippi, where he was being held on attempted murder and armed robbery charges. He was also awaiting extradition to Houston, Texas, where he’s been charged with murder, the Marshals Service said.

It wasn’t immediately clear how authorities had tracked Zimmerman to Chicago and there was no indication of any connection to the Democratic National Convention. But the restaurant he’s believed to be holed up inside is located about a half-mile from the United Center in Chicago, where the convention is being held.

Speaking to reporters on Tuesday, Smith said that Zimmerman was “barricaded inside that restaurant” and that authorities want to bring him back to Mississippi and “gather the remaining facts surrounding his escape.”