On Sunday, the gunman, who is believed to be in his 40s, entered the suburban Milwaukee house of worship around 10:25 a.m., where he shot and killed six people, mostly turbaned males, said eyewitnesses.
An Oak Creek police officer, who was credited with shooting and killing the gunman, was critically injured during the gunfire.
Shortly after the shooting, rumors that the incident was a hate crime, began to spread like wildfire.
One police spokesman said officials are treating the incident like a "domestic terrorist type situation".
According to the latest update, a total of seven people were killed and at least three people were wounded.
As of 9:13 p.m. Chicago time, two of the wounded were out of surgery and in recovery. One man was still undergoing a complex operation.
Thomas Ahern, a white ATF Agent, identified the shooter as a white male, possibly in his 40s. Other sources said the mass murderer was wearing a white T-shirt and black jeans at the time of the shooting.
President Obama, who hasn't uttered a word about the gun-related deaths in Chicago, sent his condolences to Wisconsin's Sikh community.