Numerous victims are refugees. Bones said there was no evidence that the attack was a hate crime.
The Idaho Statesman newspaper said the apartment complex catered to low-income families and was run by a Boise nonprofit. Police say they believe Kinner may have been trying to get revenge for being asked to leave the apartment complex over bad behavior.
"We saw him saying, like, bad words and stabbing a kid and a grown-up and really hard and a lot of times", Esrom said.
Kinner's return to the complex Saturday night was about seeking vengeance, Bones said.
It was unclear whether the child who died was the 3 year old girl whose birthday was being celebrated.
A three-year-old girl who was stabbed at her own birthday party in Idaho has died.
Bones did not release the names of the victims nor the ages of the adult victims injured in the attack.
Japan - World Cup - 2 July 2018
Belgium 3-2 Japan with goals from Haraguchi, Inui, Vertonghen, Fellaini and Chadli. Yet another tournament at which the Red Devils flattered to deceive.
Witnesses reported that the suspect had fled, and police arrested the 30-year-old man a short distance away.
Timmy Earl Kinner, 30, is accused of plunging a large folding knife into Ruya's body during a bloody, unexplained rampage that injured eight other people and sent waves of horror reverberating through Boise's tight-knit refugee community and beyond.
The attack is the largest stabbing in Boise history, he said. "We must come together to condemn this vile act".
Kinner, who has been charged with nine counts of aggravated battery and 6 counts of injuring a child, had previously been convicted for numerous crimes and served prison time in Kentucky, said Bones. There were no fatalities, but four of the victims were treated at a nearby hospital for what police called life-threatening injuries. "It was very violent and very frightening and there's a whole lot of trauma and hurt right now", she said. "Lives do remain in danger".
Bones said the victims were randomly targeted and had no prior connection of Kinner.
"People were scattered across the apartment complex, both within the apartments themselves, lying in the street, and in the walkways", Bones said.
The woman asked Kinner to leave due to his behavior and he left without incident, Bones said. They saw the suspect chasing people.
All nine victims were taken to a local hospital, and one seriously injured child was flown to a Salt Lake City trauma center for treatment. "Last night's horrific attack does not represent Boise", the mayor said in a written statement. "This was an attack against those who are most vulnerable".