Gabe Zimmerman had organized the outreach event at the Tucson, Ariz., supermarket where he and five others were slain when a gunman opened fire on the congresswoman and the crowd Saturday.

Ross Zimmerman told the Santa Cruz Sentinel that his son had worked with disturbed children after graduating with an honors degree in sociology from the University of California, Santa Cruz.

"It’s a strange irony that a badly disturbed child killed him," he said.

Jared Loughner, 22, made his first appearance in federal court today to face charges in the killings and the wounding of 13 others. He was ordered held without bail.

Zimmerman, a Tucson native, went on to earn a master’s degree in social work from Arizona State and shortly after began working for Giffords on her first congressional campaign in 2006.

He began working for her as a field organizer and then as constituent services director. He was working as Giffords’ director of community outreach when he was killed.

The 30-year-old was engaged to be married to Kelly O’Brien, a nurse from Yuma, Ariz. He and his fiancee had recently ran a marathon together, said Ross Zimmerman, an employee at Pima Community College, the same college Loughner attended before he was suspended.

The father and son liked to run together as well. Together, the pair completed two runs across the Grand Canyon.

"Everything was in front of him," Zimmerman said. "We are very sorry to lose him. All I ask is that people remember him."