Frazier Glenn Cross, 74, is a white supremacist who was convicted of the murders in a jury trial in September. He also has been known as Frazier Miller.
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On Tuesday, family and friends of the three killed at the Jewish sites, including a retirement home in Overland Park, Kansas, in April 2014, told the court how Cross had devastated their lives.
But "your attempt to terrorize this community has failed," Johnson County Kansas Judge Thomas Kelly Ryan said in ruling that the gunman be executed by lethal injection.
"I can't say anything more profound than what was said here today," Ryan added.
On hearing the sentence, Cross shouted at the judge. The gunman then tried to get out of his wheelchair before deputies stopped and removed him from the courtroom, KCUR reported.
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Cross, handling his own defense in court, said Tuesday he should be released because he was justified in trying to kill Jews.
"I wanted to kill Jews, not Christians," Cross said. Of those killed in his attack, none were Jewish.
Cross gave a Heil Hitler salute as he was removed from the court.
"One day my spirit will rise from the grave and you'll know I was right. I'm a happy man," he told reporters.
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