The gunman, only identified by police as a tall, bald, white man in his 40s, entered the temple Sunday morning with a 9mm semi-automatic shotgun. He was shot dead by a responding police officer outside of the temple, but not before killing many and leaving other worshippers hiding in closets in fear for their lives.

The names of the victims have not yet been released while families are still being notified. However, some members have said that the president of the congregation and a priest are among the dead.  Among the three injured being treated in Milwaukee’s Froedtert Hospital is a police officer who was shot multiple times while coming to the aid of an injured victim.

The FBI has taken over the investigation and is treating the situation as a case of domestic terrorism. According to some witnesses, though unconfirmed by authorities, the gunman bore a tattoo commemorating the September 11th attacks. The Sikh religion is often confused with Islam, though it is not the same religion.

"While the FBI is investigating whether this matter might be an act of domestic terrorism, no motive has been determined at this time," said Teresa Carlson, Special Agent in Charge with the agency's Milwaukee division, in a statement.

The FBI and a bomb squad are searching the gunman’s home, about 2.5 miles (4km) from the temple, for clues to his motive.

The Sikh religion is the 5th largest in the world, though Wisconsin only has a small population of 2,500 to 3,000 practitioners. This temple in Oak Creek, a suburb of Milwaukee, has around 350-400 members.

This event comes only two weeks after 12 were killed in the Aurora, Colorado shooting during a screening of The Dark Knight Rises.

"Our hearts go out to the families and friends of those who were killed and wounded," said President Obama in a statement released by the White House. "As we mourn this loss which took place at a house of worship, we are reminded how much our country has been enriched by Sikhs, who are a part of our broader American family."

Image: Getty