US authorities have said they are investigating reports that a gunman who killed six people at a Sikh temple in Wisconsin had white supremacist links.
Wade Michael Page, 40, who was gunned down by police during the attack near Milwaukee, reportedly performed in a white-power music group.
Five men and a woman died in the shooting. Three others including a policeman remain in critical condition.
The FBI is treating the attack as a possible domestic terrorism case.
Police chief John Edwards said they believe Page was the only shooter.
'Frustrated neo-Nazi'
Five men a woman aged between 39 and 84 were fatally shot at the Sikh Temple of Wisconsin.
Four people were found dead inside the building, and two were outside. Page was also killed outside the temple.
Chief Edwards said police officer Lieutenant Brian Murphy, 51, had been tending to a victim at the scene when he was "ambushed" by the gunman.
Lt Murphy was shot eight or nine times at "very close range", but was expected to recover.
A civil rights group, the Southern Poverty Law Center, has described Page as a "frustrated neo-Nazi".
The organisation said that in 2010 Page told a white supremacist website that he had been part of the white-power music scene since 2000.
He left his native Colorado and joined a skinhead band, End Apathy, in 2005, the civil rights organisation said.
Page entered the Wisconsin Sikh Temple temple in Oak Creek on Sunday morning and opened fire as dozens of people were preparing for a service.
He used a 9mm semi-automatic pistol, which was recovered at the scene. The weapon was purchased legally, authorities said.
'Patterns of misconduct'
US officials said Page was a former US Army member who was discharged for "patterns of misconduct" after being reduced in rank from sergeant to specialist. He was declared ineligible to re-enlist.
He was reportedly disciplined in June 1998 for being drunk on duty.
A former psychological operations specialist and a Hawk Missile System repairman, he served in the US Army between April 1992 and October 1998, ending his career at Fort Bragg, North Carolina.
On Sunday night, the authorities searched Page's house in the town of Cudahy, a few miles from the temple.
The Sikh Temple of Wisconsin in Oak Creek was founded in 1997 and is said to have a congregation of about 400 worshippers.
Indian Prime Minister Manmohan Singh, who is himself a Sikh, spoke of his shock on Monday at the shooting.
"That this senseless act of violence should be targeted at a place of religious worship is particularly painful," Mr Singh said.
Dozens of Sikhs have protested the shootings in New Delhi.
Police in New York and Chicago said they had taken additional measures to monitor Sikh temples in those cities.
Wisconsin, which passed a law in 2011 allowing citizens to carry a concealed weapon, has some of the most permissive gun laws in the US.