As the nation held candlelight vigils to remember the victims of Sunday's rampage in a Wisconsin gurdwara, investigators asserted that the gunman acted alone even as they pursued 101 leads.
Investigations so far show that discharged army veteran Wade Michael Page, who killed six worshippers at the Oak Creek Sikh gurdwara acted alone, but they continue to investigate in part because of his ties to white-supremacist groups, FBI said on Wednesday.
"I want to reiterate again that after all of this work we still have identified no one else responsible for this shooting other than him," FBI special agent in charge Teresa Carlson said at a press conference at the FBI office in Wisconsin.
"We also have not clearly defined his motive at this point," she was cited as saying by Milwaukee Journal Sentinel.
Authorities are pursuing 101 leads worldwide and have issued 180 grand jury subpoenas, Carlson said. The investigation has included more than 100 interviews that have occurred with Page's family members, associates, neighbours and employers nationwide.
Authorities also are reviewing Page's email and telephone records, state Department of Transportation video and neighbourhood security video, she said.
Citing evidence, including videotape, Carlson also made a dramatic announcement that Page shot and killed himself after he was wounded by an Oak Creek police officer.
Authorities previously said Page died after he was shot by a police officer after the gunman refused commands to drop his weapon and fired at officers. They did not mention the self-inflicted wound until Wednesday.
That officer shot Page in the stomach, "thereby neutralising the threat", Carlson said, noting: "I've seen the video, it was an amazing shot. And thank goodness."
"Subsequent to that wound, it appears that Page died of a self-inflicted gunshot wound to the head," Carlson said.
Steven Conley, assistant special agent in charge of national security for the FBI, said, "We may never know why he chose that facility at that point in time...That may have died with Page."
Carlson said Page likely came to the Milwaukee area because of a girlfriend, Misty Cook, 31, who lived in Wisconsin and who may have shared his white power beliefs.
Cook was arrested Sunday after a gun was found at their rented apartment where she continued living after she and Page broke up in June. He moved to a duplex in Cudahy, which also was searched.
But officials said they believe Cook, who also has ties to white-supremacist groups, had no role in the shootings.