CHICAGO (CBS) — Two families and groups of friends, two tragedies, but one goal. The families of Blair Holt — shot dead on a CTA bus six years ago at age 16 — and 15 year old Hadiya Pendleton — murdered not six months ago — held respective birthday celebrations for their lost loved ones.

Both were parties with a purpose. Both families are passionate about fighting the gun violence that killed their kids.

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Hadiya’s father, Anthony Pendleton, said it’s not acceptable to do nothing; then, they would become victims.

Blair’s father, Ronald Holt said one focus of the ‘Blair Holt Peace Alliance’ is to fight for common-sense gun laws, like universal background checks, and to support others who do the same.

Hadiya’s parents also have a foundation, and her friends recently started, ‘Project Orange Tree’, aimed at fighting street violence and raising awareness about how it impacts young people.

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Hadiya’s mother, Cleo Cowley-Pendleton, said members of the group wear orange buttons, the color hunters wear.

“They use the button, and the color orange as a message to say don’t shoot me,” she said.

Newly-elected Congresswoman Robin Kelly (D-IL) stopped by the Holts’ gathering to lend her support. An advocate of some gun control measures, Kelly said she told them, “I will continue to be a voice, but I cannot be a voice by myself.”

Two people have been charged in connection with Pendleton’s murder.

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Michael Pace, the man convicted of killing Holt, will spend the rest of his life in prison.