However, the police investigators are yet to determine the reason for the crime, which shocked the entire Sikh community not only in the US and India, but also globally.
Michael Wade Page, 40, died of a self-inflicted gunshot wound to the head after he killed six worshippers and wounded three others as they prepared for Sunday services at the Sikh Temple of Wisconsin in Oak Creek on Aug 5.
Investigators initially thought a responding officer killed Page with a gun shot to the stomach. But days later, authorities said Page shot himself in the head with his handgun after the officer shot and wounded Page in the abdomen.
The Milwaukee County Medical Examiner's office released its investigation report on Page yesterday and ruled that his death was a suicide. Page, a US Army veteran, had links to racist groups and was a member of a number of white power bands with names such as End Apathy and Definite Hate.
In its report, the Milwaukee County Medical Examiner's office said that Page's sister told the investigator that he had a history of alcohol problems and underwent a personality change in the year before the shooting spree.
"She stated that his demeanour had changed over the past year and he had become much more intense, as if he had lost his sense of humour and wit and perceived everything very literally," the report said.
She told the investigator that Page had moved to Milwaukee and had been living with a girlfriend and learned that they had broken up.
According to the daily, the report notes that Page had three 9mm handgun magazine clips, a box of 9mm rounds and a grip extension in a left pocket of his cargo pants.
Six 9mm casings were found around Page's body. Toxicology results, which would show whether Page was under the influence of alcohol or drugs when the shooting occurred, are not yet available, the report said.