Authorities are investigating the motivation of the gunman who killed six people in his attempt to assassinate Congresswoman Gabrielle Giffords.

Federal prosecutors have charged 22 year old Jared Loughner with 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.

FBI Director Robert Mueller says Loughner bought the Glock 9-mm handgun last year.

But he also says it's too early to speculate on his motives.

Robert Mueller, FBI Director, said, "As you can expect the investigation is barely 24 hours old and it is a little bit early to speculate on those motives."

The alleged gunman, Jared Loughner, was described by friends as a pot-smoking loner who was rejected by the Army when he tried to enlist in 2008.

Don Coorough, Jared Loughner's Classmate, said, "He's a young man who sat alone in class. He didn't appear to have any friends, certainly not in class. He didn't try to talk to anyone. He didn't try to befriend anyone. No one tried to befriend him."

On Sunday, the Pima County Sheriff's office released over 20 emergency 911 calls.

In one call, Congresswoman Gabrielle Giffords is identified as one of the victims.

Daniel Hernandez, a local student who last week started as an intern with Gifford's Tucson Congressional office was one of the first to walk to where the victims lay.

Daniel Hernandez, Intern at Giffords's Office, said, "When I arrived to where the Congresswoman and some of her constituents and staff were, I noticed that there were people down. So, what I started doing was checking pulses to see who still had a pulse."

County Sheriff Clarence Dupnik also paid tribute to the three people who helped subdue Loughner.

Clarence Dupnik, Pima County Sheriff, said, "A woman, who we have the name of but I don't have, went up and grabbed the magazine and tore it away from him. While he was trying to put another magazine in he was successful in doing that, which also had, I think, 31 bullets in it. There would have been a huge greater catastrophe had he been successful in doing that, fortunately the spring and the magazine failed and the two gentlemen were able to get it away from him and subdue him until the law enforcement people arrived."

House Speaker John Boehner said normal House business this week has been postponed in the aftermath of the shooting.

Boehner has ordered flags on the House side of the Capitol in Washington to be flown at half mast to honor Giffords' slain aide, Gabe Zimmerman.

A House Democratic leader says he thinks lawmakers should take precautions when meeting with the public in the wake of the congresswoman's shooting.