Rummel's clients included Gardena, California poker clubs, gambling ship operator Tony Cornero, and reputed mobster and convicted income-tax evader Mickey Cohen.

[3] In 1955, when unidentified gunmen shot up the home of "Bingo King" Max Kleiger in Pacific Palisades, the Los Angeles Mirror reported, "The beach front gambler's name popped up in Kefauver committee testimony here a few years ago in connection with an alleged plot to recall then Mayor Bowron so that open gambling could run in the city.

[8] Rummel was shot in the back from about ten yards distance around 1:30 a.m. on December 12, 1950, on the walkway to his home in Laurel Canyon in Los Angeles, California, United States, by someone wielding a double-barreled shotgun.

[9][10][11] The killing occurred the morning before Rummel was scheduled to testify before a grand jury in the matter of Guarantee Finance, described as a "massive bookmaking-loan syndicate that operated in county territory until it was shut down by state authorities in early 1949".

"[14] A Congressional investigation into organized crime suggested the owners of the Horseshoe Club, a rival Gardena poker outfit to Rummel's Monterey, may have had an interest in his death.