Rep. Gabrielle Giffords is responding to simple commands and is in critical condition after suffering a gunshot wound to the head yesterday, according to her doctors.
"She is able to communicate through simple commands," said Dr. Michael Lemole, a surgeon at the University Medical Center in Tucson, Ariz., who treated Giffords. "And we're very encouraged by that."
"But she's still in critical condition and brain swelling can occur at any point, but I'm cautiously optimistic," he added. "We don't know what her deficits will be in the future."
Giffords, 40, was shot in the back of her head, the bullet crossing the left side of her brain and exiting just above her left eye, said Dr. Peter Rhee, the director of Trauma and Critical Care at the University Medical Center. She is breathing with the help of a ventilator.
Fourteen other people were wounded and six killed during the assassination attempt on Giffords at a political event outside a Tucson grocery store Saturday morning.
The alleged gunman, 22-year-old Jared Loughner, is in the custody of the Pima County Sheriff's Office.
A second man whom authorities had been searching for as a person of interest in the case turned himself today in and has been released. Pima County Sheriff's Office Bureau Chief Richard Kastigar said the individual was a cab driver who had driven Loughner to the grocery store. He was caught on camera when he entered the grocery store after there was an issue with Loughner paying for the ride.
Some of the terror of that moment was evident in the 911 calls that were released today.
"Oh my god," exclaims a 911 operator who got the first report of the carnage.
A man who identified himself as Manuel Hernandez told the operator, "There was a shooting at Safeway…Where Gabrielle Giffords was…and I do believe Gabrielle Giffords was hit."
"She's hit. And I do believe she's breathing," he said. "She is breathing. She still has a pulse."
"He went in and just started firing and then he ran," said Hernandez, prompting the operator's exclamation.
A woman named Sally Badger frantically called seeking information about her husband.
"My husband just called me and told me he was shot. He was going to the Gabrielle Gifford event and I don't know where he is," Badger told 911. "He called me and then the phone went dead."
Her husband Bill Badger, a retired Army colonel, was grazed on the back of his head. He is cited by some as one of the heros who tackled Loughner to stop the slaughter.
Alleged Gunman 'Mentally Unstable'
A criminal complaint filed in federal court this afternoon charges Loughner with one count of attempted assassination of a member of Congress, two counts of killing an employee of the United States and two counts of intent to kill employees of the United States.
During a search of Loughner's home, authorities found an envelope with handwriting that read "I planned ahead," and "My assassination" and the name "Giffords," as well as Loughner's signature.
Loughner is scheduled to appear in court on Monday.
Rhee described Giffords' injury as a "devastating wound."
"Right now she's in a very good situation, and hopefully it will stay that way," he said.
Giffords is unable to open her eyes and cannot speak because of the ventilator, according to Rhee, but she is able to respond when asked to squeeze her hand or hold up her fingers.
"We take those simple commands for granted but they demonstrate high functioning in the brain," said Rhee.
Rep. Giffords was there for a "Congress on Your Corner" event, one of several events she had planned in her Arizona Congressional district to meet with her constituents.
The dead have been identified as the 63-year-old Roll, 30-year-old Gabriel Zimmerman (Giffords' director of community outreach), 76-year-old Dorthy Morris, 76-year-old Dorwin Stoddard, 79-year-old Phyllis Scheck, and 9-year-old Christina Green, according to the Pima County Sheriff's Department.
Loughner legally purchased a Glock 19- 9mm gun at Sportsman's Warehouse in Tucson on Nov. 30, law enforcement officials said. It's unclear if he bought the extended clips used with the gun during the mass shooting. An extended clip holds 30 rounds, officials said.
Pima County Sheriff Clarence Dupnik described the alleged shooter as "mentally unstable."
Dupnik lauded three individuals -- at least one of whom was shot herself -- for tackling Loughner to the ground before he was able to load another magazine into his gun.
Authorities released a photo of the other person of interest -- a white male between 40 and 50 years old with dark hair -- and said he was last seen at the event and may have a connection to Loughner.
The congresswoman was the clear focus of the gunman's assault, Dupnik said.
"He ran through the crowd and when he got to [Giffords] he just started shooting," the sheriff said.
"The anger, the hatred, the bigotry that goes on in this country is getting to be outrageous. And unfortunately Arizona I think is the capital. We are the Mecca for prejudice... for prejudice and bigotry," Dupnik said.
"When I looked up, he was shooting at Congresswoman Giffords," Steven Rayle, an eyewitness, said. "He didn't stop shooting, he just continued shooting rapidly. It was close quarters so people had nowhere to get away from."
"He didn't seem agitated, he seemed determined and just let loose with a barrage of bullets," Rayle said of the gunman.
Rayle told ABC News that "another man went running off" after the shooting, but wasn't sure if the other man was involved. Rayle said the gunman approached Giffords and shot her before turning his gun on other people randomly.
"The whole thing unfolded in about 12 or 15 seconds. As he came around it I laid down on the ground and acted as if I was shot."
Tucson Gunman: 'Defensive, Tense, Struggling'
After Giffords was shot in the head, staffers rushed to her aid, Rayle said.
"She was conscious, one of her staffers had a coat held to her face," Rayle said.
After ducking under a concrete pillar, pretending to be wounded, Rayle helped tackle the gunman. He grabbed the suspect's feet.
"He didn't really say anything except like, 'you're hurting my arm.' He was defensive, tense and struggling," Rayle said.
Giffords Had Been Target of Vandals
Giffords, a representative for Arizona's 8th District who just won reelection to a third term, has been the target of conservative political opponents in recent months.
Last March, Giffords' office was vandalized just after she voted in favor of the health care reform law. The intruders destroyed a glass door and a window at her Tucson Congressional offices.
At the time, Giffords' press secretary C.J. Karamargin said the office had received many phone calls with "nasty and rude and hateful comments" from opponents of the health care bill.
Recently Giffords, who supports gun rights, has received angry letters from anonymous sources, ranting about the supposed national gun registry and border control.
One letter received on Dec. 15 addressed to "giffords, obama, mccain and sen. Jon kyl" got personal on the topic of U.S. Border Patrol Agent Brian A. Terry, who was killed in a late night shootout at the U.S.-Mexican border.
"Brian a Terry's blood is on your hands! How many more legal residents of the USA have to die before the border is CLOSED??? Obama I call you out! CLOSE THE DAMN BORDER NOW! Quit pandering to illegals!," the letter read.
Giffords has a reputation as a political rebel. Though though she supported her party's effort to pass a landmark health reform law, she voted with the Democratic Party only about 40 percent of the time, according to Congressional Quarterly,.
She was also one of a handful of Democrats who did not vote for Nancy Pelosi for speaker of the house, during the recent Democratic leadership elections after Democrats lost their majority in the House last November.
ABC News' Rich Esposito, Pierre Thomas, Jack Date, Jason Ryan, Gina Sunseri, Ross Eichenholz, Toni Wilson, Desiree Adib, Kevin Dolka, Dean Schabner, Sherisse Pham, Amy Walter, Leezel Tanglao and the Associated Press contributed to this report.