An avowed antisemite who testified that he wanted to kill Jews and was sentenced to death after he shot and killed three people at Jewish sites in suburban Kansas City in 2014 has died in prison, the Kansas Department of Corrections said Tuesday. Frazier Glenn Miller Jr., 80, died Monday at the El Dorado Correctional Facility, where he was serving a sentence for capital murder, attempted murder, assault and firearms convictions. An autopsy will be performed to determine a cause of death, but preliminary indications were that Miller died of natural causes, Carol Pitts, a spokeswoman for the corrections department, said in a news release. She declined to comment further on Miller’s death or medical condition. The corrections department initially said it and the Kansas Bureau of Investigation would investigate Miller’s death, which is routine after an inmate dies. The KBI later said it would not investigate the death because …