OAK CREEK - A gunman killed six people and critically wounded three at a Sikh temple during Sunday services before police shot him dead, and the attack is being treated as domestic terrorism, police said.The gunman opened fire when he entered the kitchen at the Sikh Temple of Wisconsin in suburban Milwaukee at about 10:30 a.m. CDT (1530 GMT) as women were preparing a Sunday meal, witnesses said. They described the shooter as a white man.Lone gunmanWitnesses at the temple had said there was more than one gunman, but Edwards said reports of multiple gunmen were common in incidents that involved only one shooter."We believe there was one but we can't be sure," he said. Officers finished sweeping the temple only after hours of searching, and Edwards said the investigation was just starting.President Barack Obama said he was "deeply saddened" and pledged his administration's commitment to fully investigate the shooting.Obama was briefed by counterterrorism adviser John Brennan and FBI director Bob Mueller and told the situation at the temple was "under control.""The president said that he wanted to make sure that as we denounce this senseless act of violence we also underscore how much our country has been enriched by our Sikh community," the White House said in a statement.The Indian embassy in Washington said it was in touch with the National Security Council about the shooting and an Indian diplomat had been sent to the Sikh temple in Wisconsin.Milwaukee's Froedtert Hospital said three men had been brought in wounded and were in critical condition. One had been shot in the abdomen, one in the extremities and face, and a third was hit in the neck.Turban-wearing Sikhs are often mistaken for Muslims, and the Federal Bureau of Investigation is overseeing the probe into shootings, Oak Creek Police Chief John Edwards said."We're treating this as a domestic terrorist incident," he told reporters.Four people were shot dead inside the sprawling temple. Three, including the gunman, were killed outside.The gunman ambushed and shot a police officer several times when he responded to a 911 call and was helping a shooting victim, Edwards said.A second officer shot the gunman dead. Edwards had no identification of the shooter or what kind of weapon or weapons he had.The wounded officer, a 20-year veteran, was taken to a hospital and is expected to survive, he said.The Oak Creek shooting is the latest in a series of gun rampages in the suburban United States.The shooting came little more than two weeks after a gunman opened fire at a theater in Aurora, Colorado, killing 12 people and wounding 58. In January 2011, then-congresswomen Gabrielle Giffords was the target of an assassination attempt in which six people were killed and 13 were wounded."The gunman is worse than the one at the theater a couple of weeks ago because he targeted an entire community," said temple member Jagatjit Sidhu.He was among dozens of temple members and onlookers who gathered in a parking lot near the temple after police sealed the building off.