Jacob Keltner, his father Howard said, “wanted to be a soldier or policeman since he could talk.”

From a young age, Keltner – who would go on to serve 13 years with Illinois’ McHenry County Sheriff’s Office – demonstrated some of the values that defined his later career in law enforcement.

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His mother Helen told Fox News she remembered a time in middle school when other children were giving Jacob a difficult time and Howard instructed him to hit back if things got physical.

Jacob’s response?

“He said ‘No, I can’t do that,'” Helen Keltner recalled.

“He said ‘I never want my teachers to be disappointed in me and they would be very disappointed in me if I punched somebody and that’s not what I’m supposed to do,'” she added. “He always wanted to appear respectful.”

In his adult life, Keltner served in a variety of positions at the McHenry County Sheriff’s Office. He started working in patrol before becoming a detective, then switched over to a narcotics unit. Eventually, he became a member of the U.S. Marshals Service Great Lakes Regional Fugitive Task Force.

“He worked extra hours on a daily basis, and where a lot of people would put stuff off, he was ‘go go go’ all the time,” Sgt. Dan Kramer said.

But Kramer remembers March 7 – the day Keltner was shot and killed in the line of duty -- as being the “worst day I have ever experienced in my life.”

His fugitive apprehension unit was working with a U.S. Marshals Fugitive Task Force team to arrest a suspect at a hotel in Rockford, Ill., when Keltner was hit by gunfire.

Hours later, after a police chase, the suspect was in custody. But Keltner, an officer who Kramer told Fox News “did his job better than almost anyone else I know," succumbed to his injuries at a local hospital.

“He was the last guy you think would get caught, too, since he was so good,” Kramer said.

In an emotional letter written by his wife, Becki, following Keltner’s death, she described March 7 as the day she “received the one phone call every police officer’s wife has nightmares about, only this time the nightmare is real."

“Now I find myself a 33-year-old widow, mother of two young boys who no longer have their daddy,” she wrote. “It feels unreal. It’s unfair. I have screamed. I have cried.”

But she told Fox News the outpouring of support she received in the wake of her husband’s passing has been “nothing short of amazing.” She and Helen say they have received letters from local residents and strangers from around the country, with some sharing their personal phone numbers. Inside, the letters ask Keltner’s family to call if they ever need anything.

“I really wish that Jake had been there to see that in our community and just around the whole country,” Becki said.

Added Helen: “It gives you a new respect for humanity that not everyone has a bad attitude toward cops."

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Family, for Keltner, was a huge part of his life. He would build “giant forts in the basement” and “ziplines with rope” for his children, and often enjoyed swimming and having cookouts at his parents' house, Becki said. If she was having hard week herself, he would surprise her with things like secretly planned dates – always showing that he loved her.

“I think what I miss the most about him – he was always joking around, he would play practical jokes,” Becki said, noting that one of his favorites was sneaking up behind her and throwing party snaps to the ground.

In the wake of Keltner’s death, a memorial fund has been set up, shirts have been printed paying tribute to him, and at one point a local Texas Roadhouse restaurant set up a “Fallen Hero” table in his honor.

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But Becki Keltner says she has at least one wish left to fulfill – to create “a world where we stop hating each other."

“We all need to show each other love,” she wrote in her letter. “Lift each other up. It’s the only way to stop this unconscionable madness.”