ST. CLOUD, Minn. -

FBI Special Agent-in-Charge Rick Thornton said Sunday that authorities are digging into the suspect's background to determine his possible motivation for Saturday night's attack at the Crossroads Center mall in St. Cloud.

St. Cloud's mayor and police chief praised the swift actions of an off-duty, part-time Avon police officer for shooting and killing the attacker. They identified him as Officer Jason Falconer.

Mayor David Kleis says there were nine people who were hurt, not eight, as authorities previously reported.

He says the ninth person took themselves to a hospital and was treated and released.

Three of the victims remain hospitalized with injuries that aren't considered life-threatening.