An avowed white supremacist charged with killing three people outside two suburban Kansas City Jewish facilities on the eve of Passover said in a series of phone interviews that he was surprised none of the victims were Jewish.

F Glenn Miller Jr, 73, of Aurora, Missouri, told the Kansas City Star that he went to Jewish Community Center of Greater Kansas City and a nearby Jewish retirement home “for the specific purpose of killing Jews”. Miller said he learned from a newspaper story the following Saturday that the people he killed were not Jewish, the Star reported.

“I was convinced there would be all Jews or mostly Jews” at the two centres, he said, but added that the attacks still accomplished his goal of making “Jews feel less secure”.

Miller, who also goes by the name Frazier Glenn Cross Jr, is jailed in Johnson County on a charge of capital murder over the 13 April attacks. A preliminary hearing that was scheduled for last week was delayed so Miller could undergo a mental evaluation.

Miller is accused of killing Dr William Lewis Corporon, 69, and his 14-year-old grandson, Reat Griffin Underwood, who were at the community centre in Leawood for a singing contest audition. He also is accused of fatally shooting 53-year-old Terri LaManno, who was visiting her mother at the retirement home in Overland Park.

Miller said he decided to carry out the attacks because it was something he wanted to do before he died. He said he suffers from emphysema and became concerned that he didn’t have much time left during an emergency room visit in late March. He said his one regret was the death of the “young white boy”, and several times during the interviews, Miller said he thought Reat Underwood was older.

“The 14-year-old boy, he looked 20,” he said.

Miller originally said he would not speak on the record unless the Star agreed to send a copy of the recorded interview to a longtime friend of his. The Star refused, and Miller eventually consented to an interview without any conditions. Miller also reached out to the Associated Press, but after he demanded similar conditions, the AP refused the conditions and he declined the interview.

The Southern Poverty Law Center said Miller has been immersed in white supremacy most of his life. During the early 1980s, Cross was “one of the more notorious white supremacists in the US,” according to the Anti-Defamation League.

He founded the Carolina Knights of the Ku Klux Klan and served as its “grand dragon” before launching the supremacist White Patriot Party, the law centre said.

By 1987, he was the target of a nationwide manhunt for violating terms of his bond while appealing against a North Carolina conviction for operating a paramilitary camp. Federal agents tracked him along with three other men to a rural Missouri mobile home stocked with hand grenades, automatic weapons and thousands of bullets.

A federal grand jury indicted Miller on weapons charges and accused him of plotting robberies and the assassination of the law centre’s founder, Morris Dees. He then served three years in federal prison. As part of a plea bargain, he testified against other Klan leaders in a 1988 sedition trial.