Very few people survive being shot in the head at close range, but all indications are that Gabrielle Giffords is one of the lucky few.
Doctors are cautiously optimistic about her condition, but are reluctant to speculate on her recovery.
The swift response of people on the scene - emergency workers and medical staff - has been credited with saving her life in the first instance.
Daniel Hernandez, an intern on her staff, is being called a hero after he rushed to her aid - and closer to the gunman - moments after the shooting.
He applied pressure to the entry wound to staunch the bleeding, pulling her on to his lap so she would not choke on her own blood.
Paramedics then took her to a nearby hospital where trauma surgeon Peter Rhee, a former military doctor who served in Afghanistan, and his team worked with impressive efficiency.
Ms Giffords was in the operating theatre about 38 minutes after she was shot.
The bullet entered at the back of her skull and exited at the front, travelling through the left side of her brain - which controls speech among other things.