A 27-year-old Sudbury man allegedly plotted to launch terrorist attacks on shopping malls in which he and his fellow conspirators would mow down civilians with automatic weapons, federal authorities said today as they announced his arrest.

Desiring to take "some kind of action in furtherance of jihad," Tarek Mehanna and his co-conspirators allegedly had multiple conversations about obtaining weapons and randomly shooting people in malls, including discussions of the logistics of the mall attacks, assaulting from different entrances, and attacking emergency responders, acting US Attorney Michael Loucks said this morning.

Federal authorities said Mehanna's arrest early this morning at his Sudbury residence had foiled plots to launch terrorist attacks both inside and outside the United States. Read the affidavit here.

Mehanna, who faces a charge of conspiring to provide material support to terrorists, was ordered held without bail until an Oct. 30 detention hearing at his initial appearance this afternoon before US Magistrate Judge Leo Sorokin in Boston. He conspired with Ahmad Abousamra, who left the country for Syria several years ago, and others, Loucks said in a news conference today at his office in Boston.

Mehanna was first arrested and charged a year ago with lying to FBI agents in a terrorism investigation. "Today's arrest, done in conjunction with a search of his home, involves broader and more serious charges," Loucks said.

The conspirators also discussed attacking two members of the executive branch, Loucks said. Those people are no longer in the executive branch and "neither were in any danger at any time from Mehanna or his co-conspirators," he emphasized...