Authorities in the northern U.S. state of Wisconsin say a shooting at a Sikh temple Sunday morning in the city of Oak Creek, in the suburbs of Milwaukee, left seven people dead, including the gunman. Three people were wounded in the attack.

Police have described the unidentified suspect as a white male in his 40s, but have given no details or mentioned a possible motive. The local police chief said an officer exchanged fire with the gunman outside the temple and killed him.

Sunday evening, law enforcement officers extended their investigation of the shooting to a neighborhood in nearby Cudahy. They surrounded a duplex and evacuated several homes. No other details were made available, but the Associated Press quotes a federal official as saying warrants were being served at the home of the gunman.

Officials say the Federal Bureau of Investigation is involved in the investigation because the shooting might be an act of domestic terrorism.

Police say four people were found dead inside the Sikh Temple of Wisconsin. Three others, including the gunman, were killed outside the temple.

Sikhism is a monotheistic religion founded more than 500 years ago in the Punjab district of what is now India and Pakistan.

Authorities say the worldwide population of the Sikhs is 20 million with 400,000 to 1 million Sikhs in the U.S. The Sikh community in the Oak Creek area totals about 3,000 families.

The Indian embassy in Washington says it has sent a diplomat to visit the Oak Creek temple.