Indeed, the first documented race riot targeting American Sikhs occurred in 1907 in Bellingham, Wash. Their distinct religious identity (uncut hair, turban, beard) has historically marked Sikhs, particularly men, as targets for discrimination, both in their homeland in South Asia and in the various communities of the Sikh diaspora. And of course, 9/11 brought about a surge in fear and persecution directed at Sikhs, Muslims and other minorities with ties to the Middle East and South Asia.

There is also the question of whether white supremacist groups have specifically targeted American Sikhs. The authorities in Southern California, where Mr. Page was active in the white-power music scene, are investigating whether he was involved in the killings of two elderly Sikh men in Elk Grove, Calif., in March 2011. Just after the temple shooting, a Sikh man in Oak Creek, Wis., reported that a white man had pulled up next to him in a pickup truck, shaped his hands like a gun, and pretended to shoot him six times before stating, “We want to kill all of you.”

And on Aug. 15, 10 days after the Oak Creek shooting, another member of the Sikh community there, Dalbir Singh, 56, was killed in the armed robbery of a local convenience store. (While the police have not uncovered any evidence to treat the killing as a hate crime, many Sikhs have wondered if the violence was more than random.)

White supremacist Web sites clearly demonstrate intentional, targeted anti-Sikh sentiments. For example, the leading neo-Nazi figure Alex Linder was quoted as saying on a right-wing Web site: “Take your dead and go back to India and dump their ashes in the Ganges, Sikhs. You don’t belong here in the country my ancestors fought to found, and deeded to me and mine, their posterity. Even if you came here legally, and even if you haven’t done anything wrong personally. Go home, Sikhs. Go home to India where you belong. This is not your country, it belongs to white men.”

The “mistaken identity” assumption is directly associated with a second problem: a lack of data about the extent of anti-Sikh hatred.