(CNN) Jemel Roberson couldn't wait for his son's first Christmas.

With a 9-month-old boy and another baby on the way, the 26-year-old security guard was working extra shifts to buy gifts for his son and his child's mother, family attorney Lee Merritt said.

Jemel Roberson's son Tristan is now 9 months old.

During one of his shifts last weekend, a gunman started shooting up Manny's Blue Room, a bar in suburban Chicago. Witnesses said Roberson bravely stopped the shooter and pinned him to the ground.

But shortly later, a Midlothian police officer shot and killed the security guard, leaving the mother of their child in shambles.

"A family member called me and told me. ... I just broke down crying in the bathroom. For a long time, I was in the bathroom," said Avontae Boose, who's pregnant with the couple's second child.

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