MIAMI, Florida (AFP) - A Cuban-American gunman who opened fire in his apartment building, killing six neighbors, had told police he feared he was being targeted by witchcraft, police said on Wednesday.

Pedro Vargas, 42, set fire to US$10,000 (S$12,700) in cash at the start of Friday night's rampage in an apartment building in Hialeah, just outside Miami. The city is home to mostly Cubans and Cuban Americans.

"I feel threatened. And they are trying to get me with witchcraft," Vargas said in Spanish in a 12-minute call to 911 which authorities released on Wednesday.

While belief in some types of witchcraft are common in Cuba, Vargas' behavior also seems consistent with a psychotic episode with paranoid delusions - and his mother appears to have been aware of his mental condition, if unable to get him treated.

Friday his mother, aged 89, asked the 911 operator not to send police, saying that her son was having a "spell" and that what he needed was an appointment with a psychiatrist.

Vargas, a graphic designer who lived with his mother, arrived in the United States in 1997 and became a citizen in 2004.

The weapon he used, which has not been identified, was legally purchased, and Vargas had a valid licence, according to police.

Florida, which has the nation's most permissive gun laws, became the US state with the greatest number of gun owners in 2012.