Updated: 6:52 p.m.

FBI Director Robert Mueller announced Sunday that 22-year-old Jared Lee Loughner is in federal custody and will be charged in a shooting rampage that killed six people and injured 14 more, including Rep. Gabrielle Giffords (D-Ariz.).

Mueller called the shootings “an attack on our institutions and an attack on our way of life.” No further threats to lawmakers are known, he said, but “all logical precautions are in place to guarantee the safety of other public officials.”

Loughner will be charged with the assaults on Giffords and her staff; the death of Chief Judge John Roll of the U.S. District Court for Arizona; and the death of Gabe Zimmerman, Giffords’ outreach director, Mueller said.

The charges are one count of attempted assassination of a Member of Congress, two counts of killing an employee of the federal government and two counts of attempting to kill a federal employee, the Associated Press later reported.

Mueller declined to discuss specifics in the case or speculate on a motive for the attack Saturday on a gathering of constituents at a Safeway grocery store in Tucson, Ariz.

A second man who was wanted for questioning was located and cleared of wrongdoing Sunday afternoon, the Arizona Daily Star reported. Richard Kastigar, the operations bureau chief of the Pima County Sheriff’s Office, told the newspaper that the man was a cab driver who drove Loughner to the Safeway.

Mueller also declined to directly comment on whether heated political rhetoric had anything to do with the shooting.

However, he did comment on the issue in general: “Whether it’s international terror or domestic terrorism, the ubiquitous nature of the Internet means that not only threats but hate speech and other inciteful speech is much more readily available to individuals … and that absolutely presents a challenge to us particularly when it results in lone wolves or lone offenders undertaking attacks.”