By Erik Ortiz

Two days after the shooting rampage at a historic black church in South Carolina, Pardeep Kaleka left his Wisconsin home, hopped in a car and headed southeast for Charleston. The murders of nine people at the hands of a 21-year-old gunman apparently influenced by white supremacist ideology ripped open an emotional wound inside Kaleka — one that had never quite closed.

"My only regret was that I wasn't able to speak with the families of the victims and let them know there’s a whole community rallying behind them," Kaleka, 38, later told NBC News.

He felt that same communal spirit after the Aug. 5, 2012, shooting spree at a Sikh temple in the Milwaukee suburb of Oak Creek. It was a sunny Sunday morning when a man named Wade Michael Page opened fire inside the religious hall, killing six worshipers. They included Kaleka's father, 65-year-old temple president Satwant Singh Kaleka.

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The FBI described Page, who committed suicide at the scene, as a white supremacist. But his motivation for attacking the Sikh Temple of Wisconsin died with him.

"What happened in Charleston is not that different from what happened in Oak Creek," Kaleka said. "I remember the entire community, people of different ethnicities, backgrounds, races, coming to see us."

Serve2Unite founder Pardeep Kaleka with Milwaukee teacher Jacki Black and fellow Serve2Unite member, Arno Michaelis.Serve2Unite / Facebook

Kaleka says he was filled with anger after the shooting that claimed his father's life and left his mother a widow. The family had emigrated from India in 1982. It took some introspection before Kaleka, a former cop, channeled the rage and pain into something more productive: a community service group.

That same year, Kaleka and his younger brother, Amardeep, founded Serve 2 Unite, a nonprofit that works in the Milwaukee schools to foster cultural understanding and peace through art.

Joining the group was Arno Michaelis, an ex-skinhead and author of "My Life After Hate." The men met after Kaleka, struggling for answers, was introduced to him through an anti-violent extremism network.

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Kaleka tells the schoolchildren that they can make choices for the better, and not to think the only answer is wielding a weapon.

"We sometimes don't have a choice about what happens to us, but generally, you have a choice in how you respond," Kaleka said. "You realize that if something bad happens, you have more than one choice in what to do."

Arno Michaelis and Pardeep Kaleka speak to Milwaukee-area schoolchildren.Serve2Unite

In the wake of Charleston and other similar attacks, retaliating physically doesn't solve anything, he tells the students.

"If you think about the motive that the person had, their motive was hatred and they came into a place to divide," Kaleka said. "If you respond in that same way, who actually wins?"

The unity that bound Oak Creek residents following the shooting has stayed with Kaleka. In return, he said, the Sikh community — once very insular — has made an effort not to self-segregate and to open up dialogue with other groups.

Since the shooting, he has seen his efforts make a difference through an annual 6K run/walk in honor of the six victims. This year's race is planned for Aug. 1, and the proceeds again go toward a scholarship fund for local high school students.

"With each one of these (shooting) incidents, there's a little bit of hope that people can come together," Kaleka said, "and know that we all have a responsibility to eliminate hate."