SWAT officers surround a Sikh temple in Oak Creek, Wisconsin, where a gunman stormed the service and opened fire on Sunday, August 5. The incident left six people and the gunman dead. 
SWAT officers gather in front of the temple on Sunday. The attack occurred about 10:30 a.m. (11:30 a.m. ET), when temple members were reading scriptures and cooking food. 
Police work outside the entrance to the temple, which is near Milwaukee. 
People wait for word on family and friends in front of the Sikh temple. The Oak Creek temple, or gurdwara, opened in 2007. 
A police officer directs people near the temple. 
A tactical officer runs to position as SWAT officers surround the temple. 
Police man an armored vehicle outside the temple. - The name of the shooter may be released as early as Monday morning
- Those inside the temple say the man had a 9/11 tattoo on one arm
Oak Creek, Wisconsin (CNN) -- The gunman who shot six people to death and wounded three others during a rampage at a Sikh temple in a Milwaukee suburb was an Army veteran who may have been a white supremacist, according to a law enforcement source involved in the investigation.
The name of the shooter, who himself was killed by police, may be released as early as Monday morning, the source added.
Earlier, the FBI had said it had not determined a motive for the Sunday morning shooting and that investigators were looking into whether the attack might be classified as domestic terrorism.
Tom Ahern, a spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the gunman had a military background but would not elaborate. He also would not elaborate on the man's tattoos.
Kanwardeep Singh Kaleka, a member of the five-year-old temple in Oakcreek, Wisconsin, said those inside the gurdwara -- or Sikh house of worsip -- described the attacker as a bald, white man, dressed in a white T-shirt and black pants and with a 9/11 tattoo on one arm -- which "implies to me that there's some level of hate crime there."
Because of their customary beards and turbans, Sikh men are often confused for Muslims, and have been the targets of hate crimes since the September 11, 2001, attacks on New York and Washington.
CNN's Brian Todd, Harmeet Shah Singh, Poppy Harlow, Ed Payne, Ted Rowlands, Marlena Baldacci, Matt Smith, Steve Almasy, Greg Botelho, Shawn Nottingham, Carol Cratty, Susan Candiotti and Deborah Feyerick contributed to this report.
