At least four people were killed and seven more wounded Wednesday when a man went on a stabbing rampage in a northern Illinois, U.S., the police said.

A 22-year-old man is in police custody and was being questioned, according to Rockford Police Chief Carla Redd. She said one of the people who was wounded remained in critical condition.

"My heart goes out to the families right now that are suffering a loss," Redd told reporters.

She said the Rockford Police received a medical call at 1:14 p.m. followed by additional calls for police and paramedics.

"We don’t believe there’s any other suspects that are on the run or at large at this particular time," Redd said. "Right now, we don’t have a clear motive as to what caused this individual to commit such a heinous crime."

Not all of the victims found at multiple addresses in the city had stab wounds and none were shot, according to Redd.

Rockford Police initially said five people had been injured. Cori Hilliard, a public information officer with the Winnebago County Sheriff’s Office, told the Associated Press Wednesday evening that two more victims were among those hurt.

Three people died at the scenes. The fourth died at a hospital.

Police later identified those victims as a 15-year-old girl, a 63-year-old woman, a 49-year-old man and a 22-year-old man. Their names were not released.

Redd said residents in the area were being asked to review their home surveillance camera footage for anything related to the attacks.

Rockford’s population is about 150,000 and it’s 145 kilometers (90 miles) northwest of Chicago. The violence Wednesday came days after a teenage employee of a Walmart in Rockford was stabbed and killed inside the store.