A federal prosecutor has claimed that the white supremacist and homophobe charged with shooting dead three people at Jewish centres near Kansas City earlier this month was once caught having sex with a black male prostitute.

Prosecutor Doug McCullough said he made the discovery while investigating alleged killer Frazier Glenn Miller in 1987, adding that it was “pretty shocking, because of personal stances that he had taken and what he is now accused of engaging in”.

Meanwhile, it emerged this week that while he was on the run in 1987, Miller had sent a two-page manifesto to white supremacists and other sympathisers, urging them to follow in his footsteps as he “declared war on Niggers, Jews, Queers”.

In the manifesto, Miller also called for the mass-slaying of Jews in a “Declaration of War.”

It read: “The Jews are our main and most formidable enemies,” and set out a ‘points system’ for different assassination targets: “Niggers (1)... Jews (10), influential Jews (25).”

The manifesto was found in Miller’s trailer along with a large cache of weapons just before he was arrested in 1987.

The call for mass-murder was not Miller’s first brush with the law; in a prior lawsuit launched against him in 1984, he admitted terrorising an African-American family.

The North Carolina native, now 73, founded and ran the Carolina Knights of the Ku Klux Klan and the White Patriot Party in the 1980s.

His alleged shooting rampage in Overland Park, Kansas City, last month has fuelled nationwide concerns about a rise of antisemitism.

The Jewish community centre where one of the attacks took place is phasing in new security measures.

An “armed presence” is planned for most of the centre’s operating hours and a security director will be hired “as soon as possible”, according to a report in the Kansas Star.