Arizona State Rep. Matt Heinz, D-Tucson, said the fact that Hernandez was nearby and able to react quickly after she was shot Saturday probably saved Giffords' life, the Arizona Republic reported.
Giffords was among those injured in a shooting rampage that left six people dead at a "Congress on Your Corner" event she hosted in Tucson. The FBI has charged 22-year-old Jared Lee Loughner in the shootings.
Hernandez, a 20-year-old junior at the University of Arizona, was about 30 feet away from Giffords when he heard gunfire and rushed toward the congresswoman.
"I don't even know if the gunfire had stopped," Hernandez said. "It was probably not the best idea to run toward the gunshots, but people needed help."
Hernandez said he saw several people on the ground bleeding and that he moved from person to person checking for pulses. He said he saw a bleeding Giffords lying on the sidewalk.
Using his hand, he applied pressure to one of her wounds and he pulled her into his lap so she wouldn't choke on her own blood. He stayed with Giffords until emergency medical personnel arrived.
Hernandez, who had been an intern for Giffords for just five days when the shooting occurred, stayed with her in the ambulance ride to the hospital.
"I was ecstatic," Hernandez said after learning Giffords survived brain surgery. "She was one of the people I've looked up to. Knowing she was alive and still fighting was good news. She's definitely a fighter, whether for her own life, or standing up for people in southern Arizona."