Cahill, a 62-year-old physician assistant of Cameron, Texas, suffered a heart attack two weeks ago and returned to work at the base as a civilian employee after taking just one week off for recovery, said his daughter Keely Vanacker. "He survived that. He was getting back on track, and he gets killed by a gunman," Vanacker said, her words bare with shock and disbelief.

Cahill (pictured, left, with his grandson Brody) helped treat soldiers returning from tours of duty or preparing for deployment. Often, Vanacker said, Cahill would walk young soldiers where they needed to go, just to make sure they got the right treatment. "He loved his patients, and his patients loved him," said Vanacker, 33, the oldest of Cahill's three adult children. "He just felt his job was important."