US Representative Gabrielle Giffords of Arizona was shot in the head Saturday when an assailant opened fire outside a grocery store during a meeting with constituents killing at least five people.

The hospital says Giffords' outlook is "optimistic" and she's responding to commands from doctors. At least 10 people are said to have sustained injuries and according to reports a 9-year-old child and federal judge John Roll were among those killed.

Officials say the FBI and local law enforcement agents are investigating the attack, which took place while Giffords was greeting constituents outside a Tucson grocery store.

Police say the shooter is in custody, and has been identified by people familiar with the investigation as 22 year old Jared Loughner. Pima County Sheriff's officials say he used a pistol to carry out the shooting spree.

The shooting prompted an outpouring of sympathy from politicians and people around the country. Obama called the shooting "an unspeakable tragedy" and that such "a senseless and terrible act of violence has no place in a free society." Obama has sent his FBI director to oversee the investigation.