Georgia police sought further clues on Thursday to the motive in the fatal shootings of eight people, six of them Asian women, at Atlanta-area spas, as Asian-American leaders testified to the US Congress about the proliferation of hate crimes targeting the group.

President Joe Biden ordered that the US flag be flown at half-staff at the White House to honour the victims of Tuesday’s rampage, for which Robert Aaron Long has been charged with eight counts of murder at two spas in Atlanta and one in Cherokee County about 64km to its north.

Long, a 21-year-old white male, suggested to investigators that a sex addiction led him to violence. But authorities have not ruled out the possibility that the attacks were motivated at least in part by some other grievance, including anti-Asian sentiments.

“Our investigation is far from over and we have not ruled anything out,” the Atlanta Police Department said in a statement.

The shootings triggered an outcry from civil rights advocates and some political leaders, including Biden, who condemned a rise in incidents of anti-Asian discrimination and violence since the beginning of the Covid-19 pandemic. Lawmakers and civic leaders were testifying before a House of Representatives Judiciary subcommittee on the increase in anti-Asian discrimination and violence.