A gunman opened fire at a country music festival on the Las Vegas Strip on Sunday, killing at least 20 people and wounding more than 100 others before the shooter was killed by police.
Police described the suspect as being a local Las Vegas man who acted alone and was not believed to be connected to any militant group, Clark County Sheriff Joseph Lombardo told reporters.
“We have no idea what his belief system was,” he said. “Right now, we believe he was the sole aggressor and the scene is static.”
Authorities were seeking a woman they named as Marilou Danley, he said. He gave no details of whether she was suspected of involvement in the attack but described her as an “associate”.
He said rumours of other shootings or explosives such as car bombs in the area were false.
Las Vegas is a major resort city, known primarily for its gambling, shopping and nightlife, which would have been packed at time the shooting broke out shortly after 10 p.m. (0400 GMT).
And police said the toll may yet rise: “I don’t want to give you an accurate number because I don’t have it yet,” Lombardo said.
The shooting broke out on the last night of the three-day Route 91 Harvest festival, a sold-out event attended by thousands and featuring top acts such as Eric Church, Sam Hunt and Jason Aldean.
U.S. media, including Fox News, reported that Aldean was performing when the rampage began but that he had been bundled safely off stage at the event outside the Mandalay Bay Resort and Casino in the Nevada gambling mecca. CNN reported all the artists were safe.
Lombardo said the gunfire came from the 32nd floor of the Mandalay Bay, where the gunman was killed.
Police have disclosed no information that would suggest a motive for the shooting or revealed the identify of the suspect.
Even so, the rampage was reminiscent of a mass shooting at a Paris rock concert in November 2015 that killed 89 people, part of a coordinated attack by Islamist militants that left 130 dead.
A witness named Christine told CNN both she and her husband had separately taken shooting victims to two hospitals, the University Medical Center and the Sunrise Hospital and Medical Center.
“The shots just kept coming,” she said. “Everyone was telling us ‘run, run as fast as you can’.”
Off-duty police were believe to be among the victims, the sheriff said.
The concert venue was in an outdoor area known as Las Vegas Village, across the Strip from the Mandalay Bay and the Luxor hotels.
The Mandalay Bay hotel is near McCarran International Airport, which said on Twitter it had temporarily halted flights after the shooting. Later, the airport said that some flights had resumed.