Detectives with the Pima County Sheriff's Department interviewed the "person of interest" in Saturday's mass shooting and cleared him of any wrongdoing.

The man, a cab driver, told detectives he gave Jared Lee Loughner a ride to the Safeway and they entered the store together so Loughner could obtain change to pay his fare, said Bureau Chief Richard Kastigar.

Records substantiate the driver dropped Loughner off at 9:59 a.m., Kastigar said.

The first report of a shooting came in 10:11 a.m. and paramedics were on scene at 10:16 a.m., Kastigar said.

FBI Director Robert Mueller announced this morning he anticipates federal charges will be filed this afternoon against Loughner in the death of U.S. District Judge John Roll and the shootings of Rep. Gabrielle Giffords and her staff members.

Discussions are under way as to the filing of state charges in regards to the other victims, Mueller said.

Authorities also today released more gripping details of the event that killed six people and wounded 14 others at a Congress on Your Corner event.

Seconds after Loughner emptied the clip of a 9 mm Glock into the crowd at Safeway, one of the women he shot grabbed the magazine in an effort to stop him, Pima County Sheriff Clarence Dupnik said this morning.

"The woman went up and grabbed the magazine and tore it away from him," Dupnik said.

Loughner was able to insert a second, 31-round magazine, but because the gun malfunctioned and two men tackled him, a "greater catosphere" was averted, Dupnik said.

The names of the three heroes have not yet been released.

Mueller and Dupnik said Loughner attended a 2007 Congress on Your Corner event after exchanging correspondence with Giffords' office and being extended an invitation. Authorities continue to work around the clock to determine why Loughner committed such a "heinous act," Mueller said.

When asked if Dupnik would classify the incident as a hate crime, he said: "You could probably call most murders a hate crime."

Mueller said he was not discounting the possibility of charging Loughner with crimes under domestic terrorism statutes, but said it was "premature to say what the motivations were or to draw generalizations."

A suspicious package found at Giffords' office following the shootings did not contain any explosive materials, but investigators are looking into who sent the package and why, Mueller said. FBI lab analysts will attempt to obtain DNA and fingerprints from the package, he said.

Loughner purchased the Glock from a gun store in November, Mueller said. He was not legally prohibited from purchasing the gun.

Contact reporter Kim Smith at 573-4241 or