The death of John M. Roll has unnerved colleagues, friends and other public officials who not only have to deal with the personal loss but also that of a chief judge responsible for leading Arizona's U.S. District Court.

An internal law enforcement memo obtained by Fox News reveals that the respected and beloved federal judge accepted a late invitation to attend Saturday's informal public meeting organized by Democratic Rep. Gabrielle Giffords. The spur of the moment decision sent Roll, a George H.W. Bush appointee, to the parking lot of his neighborhood shopping center and into an ambush that took his life and the lives of five others.

"I had just had lunch with him. In fact we were going to have lunch again on Tuesday," Arizona Sen. Jon Kyl, a Republican, said Sunday on CBS' Face the Nation. "But I just have to say that first of all for those who were killed they leave behind grieving families. And Judge Roll's loss is going to be particularly important for the Arizona judiciary. ... We have one of the top three districts in terms of caseloads, and it took a lot of his time to try to meet the responsibilities of the court especially with all of the drug and immigration cases."

Washington D.C. lawyer Matt Bowman did a two-year clerkship for Roll from 2003-2005. He applied on the hope that their common membership in the Knights of Columbus might work to his advantage. They first met during Bowman's job interview.

"He rolled out the red carpet for me as if I was the important person there," Bowman recalled in a phone interview with Fox News on Sunday.

In addition to running his courthouse, Bowman said Roll was a widely respected authority on criminal trial procedures. Roll's book on the subject is considered the authoritative resource for judges presiding over criminal trials.

Bowman called Roll an excellent lawyer but more importantly, "a Christian, husband and father."

Roll played a key part in recommending Bowman for a subsequent clerkship with now Supreme Court Justice Samuel Alito.

"I owe, really my career and my understanding on how to be a lawyer to Chief Judge Roll," Bowman said.

Roll spent nearly 20 years on the federal bench. He was appointed by Bush in 1991 and eventually became chief judge of the Arizona federal courts. A notice on the court's website called him a "devoted husband, father of three, grandfather of five, and friend to all who knew him, will be greatly missed by his family and community."

Federal officials on Sunday filed murder charges against Jared Lee Loughner. The 22-year old is scheduled to appear before a magistrate judge Monday afternoon in Phoenix.