A man who's bad behaviour prompted him to be asked to leave a US apartment building returned the next day and stabbed nine people, including six children, at a three-year-old's birthday party, police say.
Refugees from Syria, Iraq and Ethiopia were among the injured in Saturday night's attack in Boise, Idaho.
Boise Police Chief William Bones said that while the suspect is an American, investigators have not found any evidence to indicate it was a hate crime, but investigations are continuing.
"This incident is not a representation of our community but a single evil individual who attacked people without provocation that we are aware of at this time," Bones said on Sunday.
Police say a woman had offered Timmy Kinner, 30, a temporary place to stay as he was new to the area but on Friday asked him to leave, which he did peacefully.
But police say Kinner returned the following day and targeted a toddler's birthday party being held nearby to where he had been staying.
The victims included the three-year-old birthday girl and five other children aged four to 12. Three adults who defended them were also hurt, some seriously, Bones said. The woman who had offered him accommodation was not hurt.
"I believe her perception was, 'Here's a helping hand I can give in return for a helping hand I have been given,"' Bones said of the woman.
Esrom Habte, 12, and Fathi Mahamoud, 11, were playing outside when the attack began.
"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.
The pair ran inside and hid in a cupboard until police said it was safe to come out, he said.
Kinner was arrested near the scene and charged with aggravated battery and of injury to a child. The knife was found dumped in a nearby canal, police say.
Mayor Dave Bieter condemned the attack on Twitter.
"Last night's horrific attack does not represent Boise," Bieter wrote.
"Please join me in praying for the injured and their families. We must come together to condemn this vile act."
Megan Schwab, who works with the International Rescue Committee in Boise, said the organisation was working to provide temporary housing, counselling and other support to those affected by the attack.
