(CNN) Greg Zanis' 26,275 crosses have been seen at nearly every national tragedy since Columbine. Now, five more stand in his hometown.

He knew something was wrong when dozens of law enforcement vehicles, sirens screaming, rocketed by his Aurora, Illinois, house on Friday afternoon. About 15 minutes later, Zanis' daughter called saying there was an active shooter.

"I guess I never thought it could possibly happen here," Zanis says solemnly.

Most Americans probably don't know his name, but many have has seen Greg Zanis' work — painted crosses with victims' name enscribed on them — erected after a national tragedy.

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