Four individuals have lost their lives, and a minimum of five others have sustained injuries following a rampage by a knife-wielding man in Illinois, USA.

Rockford police reported that the assaults transpired subsequent to a home invasion on Wednesday afternoon, with one of the wounded individuals currently in critical condition.

The victims encompass a 15-year-old girl, a 63-year-old woman, a 49-year-old man, and a 22-year-old man.

A 22-year-old suspect has been apprehended and is undergoing interrogation by law enforcement authorities.

The motive behind the attacks remains unclear, according to police statements.

The initial home invasion took place on Florence Street, although the incidents unfolded across various locations, as indicated by police reports.

Winnebago County Sheriff Gary Caruana stated that a young woman sustained stab injuries to her hands and face while attempting to flee from the assailant and is presently hospitalized, undergoing intubation.

Additionally, another individual described as a "good Samaritan" by Sheriff Caruana sustained less severe stab wounds after intervening to aid the fleeing woman.

Rockford Police Chief Carla Redd said that not all of the victims had been stabbed, but added that none had suffered gunshot wounds.

She said police did not believe there were any other suspects at large.

"Words can't even express my thoughts right now..." she said. "My heart goes out to the families right now who are suffering a loss."

Rockford resident Ruth Gallagher told CBS her long-time postman was among the dead, while the US Postal Service confirmed that a postman had been killed.

"He was the kindest person," Ms Gallagher said. "He would help anybody, would step in and help. Always friendly. It's just devastation for all of us. It's just a nightmare."

In a statement, Rockford city mayor Tom McNamara said his heart was "breaking for those who have lost their lives, their families and our community".

"This is, obviously, a huge blow to all of us," he said. "However, in Rockford fashion, we get knocked down, sometimes too much, but we always get back up stronger."

He added that free counselling services would be made available on Thursday and Friday at Flinn Middle School in Rockford.