Tattoos on the body of the slain Sikh temple gunman and certain biographical details led the FBI to treat the attack at a Milwaukee-area temple as an act of domestic terrorism, officials said Sunday.

[...] A federal official who spoke on the condition of anonymity because he was not authorized to speak to the media refused to say whether the gunman was thought to belong to a hate group or some other violent group because the investigation was still unfolding.

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At least seven people, including a gunman shot by a police officer, have been killed in an attack on worshipers at a Sikh temple in the Milwaukee suburb of Oak Creek, Wisconsin, police have said.