Police in the US state of Georgia have identified four of the eight people who were killed in shootings at three massage parlours in the Atlanta area.
Officials say it is still too early to know whether the attack, in which six Asian women were killed, was racially motivated.
Cherokee County Sheriff Frank Reynolds said the suspect may have been a patron and claimed to have a "sex addiction".
The alleged gunman has been charged with counts of murder and assault.
The attack comes amid a sharp uptick in crimes against Asian-Americans.
Four of the victims have been identified as Ashley Yaun, 33; Paul Andre Michels, 54; Xiaojie Yan, 49; and Daoyou Feng, 44. Elcias R Hernandez-Ortiz was identified as having been injured.
What did police say?
In a news conference on Wednesday (local time), investigators said suspect Robert Aaron Long admitted to the shooting spree, and said that he denied that the attack was motivated by race.
Long has been charged with four counts of murder and and one count of aggravated assault, according to the Cherokee County Sheriff's Department.
"He apparently has an issue, what he considers a sex addiction, and sees these locations as a temptation for him that he wanted to eliminate," said Captain Jay Baker, adding that Long was caught with a 9mm handgun and did not resist arrest.
Massage parlours are known to sometimes provide prostitution services, but authorities say there is no indication yet that this is the case at the targeted locations.
"These are legally operating businesses that have not been on our radar," said Atlanta Mayor Keisha Lance Bottoms, who added that the city would not engage in "victim shaming, victim blaming".
Police also noted it is still too early in the investigation to definitively state a motive and that the suspect appeared to have been acting alone.
Bottoms said that Long was on his way to Florida, possibly to commit more shootings, when he was arrested.
The suspect's parents helped to identify him, officials told reporters.
According to CBS News, the suspect told investigators that "he loved God and guns".
What do we know about the shootings?
The first happened at about 21:00GMT on Tuesday at Young's Asian Massage in Acworth, Cherokee County.
Two people died at the scene and three were taken to hospital, where two more died, sheriff's office spokesperson Captain Jay Baker said. He later confirmed the victims were two Asian women, a white woman and a white man, and said a Hispanic man had been wounded.
Less than an hour later, police were called to a "robbery in progress" at Gold Spa in north-east Atlanta.
"Upon arrival, officers located three females deceased inside the location from apparent gunshot wounds," police said.
While there, officers were called to a spa across the street, called Aromatherapy Spa, where they found another woman shot dead.
Investigators who had studied CCTV footage then released images of a suspect near one of the spas. Police said that, after a manhunt, Robert Aaron Long, of Woodstock, Georgia, was arrested in Crisp County, about 240km south of Atlanta.
Authorities in South Korea said they were working to confirm the nationalities of the four women of Korean descent.
What has the reaction been?
Though authorities say it is too early to know if the victims were targeted because of their race, many online have criticised a recent rise in anti-Asian hate crimes, which activists have linked to rhetoric blaming Asian people for the coronavirus pandemic.
The advocacy group Stop AAPI Hate, which tracks attacks on Asian Americans and Pacific Islanders acknowledged a motive was unclear, but said "right now there is a great deal of fear and pain in the Asian American community that must be addressed".
It called the shootings "an unspeakable tragedy" for both the victims' families and the Asian-American community, which has "been reeling from high levels of racist attacks".
"A motive is still not clear, but a crime against any community is a crime against us all," Mayor Bottoms said in a statement, adding that she had been in communication with the White House.
President Joe Biden said he had been briefed on the shootings. Ahead of his meeting with the Irish prime minister, the president acknowledged that "Asian-Americans have been very concerned" but would not speculate on the gunman's motive.
"I'll have more to say when the investigation is completed."
Vice-President Kamala Harris, the first Asian-American to hold the office, said during a Wednesday meeting with Irish officials: "I do want to say to our Asian-American community that we stand with you and understand how this has frightened and shocked and outraged all people."
Ben Crump, a leading civil rights lawyer, also took to Twitter, saying: "Today's tragic killings in #Atlanta reaffirm the need for us to step up and protect ALL of America's marginalised minorities from racism."
Atlanta police said they were increasing patrols around businesses similar to those attacked.
The New York Police Department's counter-terrorism branch said that while there was no known connection to New York city, it would "be deploying assets to our great Asian communities across the city out of an abundance of caution".
The police department in Seattle also said it would increase patrols and outreach to support its Asian-American community.
Georgia Governor Brian Kemp praised law enforcement officials for their response to the shootings, and said: "Our entire family is praying for the victims of these horrific acts of violence."
US Secretary of State Antony Blinken addressed the shootings ahead of a meeting with his South Korean counterpart on Wednesday. "We are horrified by this violence which has no place in America or anywhere," he said.
"We will stand up for the right of our fellow Americans, Korean Americans, to be safe, to be treated with dignity."