Eight people, including children, were shot and killed by a gunman on Saturday at a mall north of Dallas in Texas.
As eyewitnesses recounted a guy firing randomly at onlookers, hundreds of people were forced to flee the Allen Premium Outlets complex, international media reported.
After hearing shots, a policeman responding to an unrelated incident shot and killed the gunman.
Authorities have not yet zeroed in on a specific motive, but investigators uncovered an extensive social media presence by the gunman, including a possible link to right-wing extremism, a senior law enforcement source familiar with the investigation told CNN.
In the wake of the tragedy, President Joe Biden again called on Congress to strengthen gun laws on Sunday.
He said the attacker, using an AR-15 style assault weapon, gunned down innocents in “the latest act of gun violence to devastate our nation”.
“Such an attack is too shocking to be so familiar,” he added, calling on Congress to ban assault weapons and high-capacity magazines, and require universal background checks.
As of Sunday morning local team, at least three surviving victims were in critical condition, police said.
Allen Fire Chief Jonathan Boyd said seven people – including the gunman – were pronounced dead at the scene and two died later in hospital.
The victims’ ages range from 5 to 51, BBC reported quoting the hospital spokesperson.
A police officer at the mall “heard gunshots, went to the gunshots, engaged the suspect and neutralised the suspect,” Allen Police Chief Brian Harvey told the news organisation.
Some witnesses described the gunman as dressed all in black and wearing combat gear. Footage taken after the gunman’s death appeared to show an AR-15 style rifle lying near his body.
Texas Governor Greg Abbott described the shooting as an “unspeakable tragedy” and said the state was ready to offer any assistance to local authorities.
US police have asked members of the public with video captured at the scene to contact the FBI, as they collect evidence.