(CNN) - Gabe Zimmerman, Rep. Gabrielle Giffords' director of community outreach, was among those killed Saturday in the Arizona shooting, Giffords' Communications Director C.J. Karamargin told CNN.
Zimmerman was in Tucson with Giffords conducting a "Congress On Your Corner" event, which is an opportunity for constituents to meet their representatives.
Colleen Kennedy, 44, who lived next door to Zimmerman and his fiance in Tucson's Orchard River Townhomes, said she heard about the shooting on the radio and remembered that Zimmerman worked for the congresswoman.
"At 11 I went over to the house. She had music on," Kennedy said. "I asked her, 'Does Gabe work for Gabi Giffords?' She said 'Yes.' Then I asked her, 'Has he called you?' She said 'No.' I said, 'You should try to call him right now.'"
Kennedy said when Zimmerman didn't answer, she suggested the fiancé call his colleagues.
"I heard her ask if Gabe was OK, but they had no details," she said.
Nancy Harris, another neighbor, described Zimmerman as "very polite" and "friendly."
"It's heartbreaking," she said. "He was just a nice young man with a nice future - newly engaged, and I'm sure looking forward to life."
Pia Carusone, Giffords' chief of staff, released a statement soon after the attack.
"An unthinkable tragedy occurred at our Congress On Your Corner event today in Tucson," she said. "Our community has lost beloved friends and colleagues, and many more are injured. Our hearts and prayers go out to all of them and to those who are suffering the loss of treasured friends and family members."