Wilcox saw the shooters at the Wal-Mart on June 8 and pulled out his legally concealed handgun to stop them, but was shot by Amanda Miller. He was returning computer equipment at the time. The Millers died after a shootout with police at the store.
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Sheriff Doug Gillespie eulogized Wilcox as a hero, saying his actions allowed other shoppers to safely leave the store.
"He made the decision to put his life in danger to help hundreds of others in the store," Gillespie said. "He is a man friends and family and the entire community should be proud of."
Steve Withey, associate pastor at the GV Christian Center, agreed.
"Joseph exemplifies what it means to fear no evil ... His courage is what we honor the most today," he said.
Las Vegas City Councilman Bob Coffin noted Wilcox, a lifelong Las Vegas resident, was awarded a posthumous Medal of Valor from the council.
"It's been controversial that Joseph carried a weapon," he said. "But Joseph followed the rules."
The service ended with the family thanking the community for its support.
"The day we lost Joseph, our lives changed forever," the family said in a statement. "Each day is difficult, but the overwhelming love, words of encouragement and financial support you have graciously given us has made this life-changing moment a little less difficult.
"Our hearts ache, but we are not alone — our thoughts are with the family and friends of Officer Beck and Officer Soldo as they, too, try to continue their lives without their loved ones."
Wilcox was in a check-out aisle when the assailants entered the Wal-Mart. After Jerad Miller fired a shot into the air, Wilcox drew his gun and approached him from behind. But Wilcox was unaware that a short distance away was Amanda Miller, who killed him.