Federal agents and detectives from the D.C. Metropolitan Police Department have launched a broad and multipronged investigation into the mayhem and death Wednesday at the United States Capitol, that sources tell ABC News includes an effort to determine the motives of a paramilitary faction of the mob that invaded the heart of American government.

“We’re talking about a very complex investigation,” said Robert Boyce, a 35-year veteran and former chief of detectives of the New York Police Department.

Investigators have begun the painstaking task of unwinding and documenting the events of Jan. 6, as thousands of pro-Trump rally-goers crossed the National Mall, overran Capitol Police metal barricades, and barged through the hallowed halls of the U.S. Capitol building. In the chaos, five people died, including Capitol Police officer Brian Sicknick.

That effort involves scanning volumes of social media posts, reviewing hours of security camera footage, and combing through mountains of cellphone data to determine exactly what occurred, investigators told ABC News.

Already, the Department of Justice has announced numerous arrests of intruders, including one who posted photos of himself seated at House Speaker Nancy Pelosi’s desk.

“The idiots who self-identify will be the first to go,” Boyce said.

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