Durbin said Dr. Jerry Umanos, Gary Gabel and his son John represent the best of who we are as a people.
They were killed when an Afghan security guard opened fire at a hospital in Kabul.
Umanos was a pediatrician, the Gabels were visiting him.
"I'm sure my colleagues join me in expressing our heartfelt condolences to families and loved ones of those lost and injured in this tragic attack," Durbin said.
It's unclear what caused the guard to shoot the three men. He shot himself but survived and at last word was in police custody.