The suspect in a mass stabbing in Boise, Idaho, targeted a 3-year-old girl's birthday party when he injured nine people, including six children, at an apartment complex home to many refugee families, police said Sunday.

Timmy Kinner, 30, of Los Angeles was arrested late Saturday and charged with nine counts of felony aggravated battery and six counts of causing injury to a child — also a felony.

"Our victims are some of the newest member of our community," Boise Police Chief Bill Bones said at a news conference Sunday, adding that those hurt in the attack had fled violence in Syria, Iraq and Ethiopia.

Timmy Kinner, 30, the suspect in the stabbings at an apartment complex in Boise, Idaho. Courtesy Ada County Sheriff's Office / Reuters

Kinner had been staying with a woman at the Wylie Street Station Apartment Complex, who opened her home to him as a gesture of goodwill, Bones said.

The woman asked Kinner to leave due to his behavior and he left without incident, Bones said. However, on Saturday, Kinner returned "to extract vengeance," Bones said. Bones did not specify what behavior led the woman, who was not injured in the stabbing, to ask Kinner to leave.

Saturday evening's attack left the 3-year-old, who was having a birthday party, two 4-year-olds, a 6-year-old, an 8-year-old, a 12-year-old, and three adults injured.

"The crime scene, the faces of the parents struggling, the tears streaming down their faces, the faces of children in hospital beds will be something I will carry with me for the rest of my life," Bones said.

On Sunday, Bones' voice caught with emotion as he explained that while those injured are expected to survive, some will suffer "life-changing" injuries. He said one child was transferred to a hospital in Salt Lake City for treatment.

"It doesn't just tug at your heart strings, it tears your heart apart," Bones said.

Bones did not release the names of the victims nor the ages of the adult victims injured in the attack.

Kinner has an extensive criminal history, Bones said, but had not been previously arrested in Boise. He said that police currently don't have evidence that the attack was a hate crime, but investigators are still working to make that determination.

The attack resulted in the most victims in a single incident in Boise Police Department history, Bones said.

"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.

Police received a report of a stabbing at 8:46 p.m., and responded to the apartment complex within four minutes, Bones said. They found victims in the parking lot and inside the apartment complex.