A man armed with a knife went on a rampage in the US state of Illinois, resulting in the deaths of four people and injuries to at least five others.

The attacks followed a home invasion in Rockford on Wednesday afternoon, with one of the injured individuals in critical condition.

Among the victims are 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 currently undergoing questioning by police, though the motive for the attacks remains unclear. While the home invasion occurred on Florence Street, the attacks unfolded across multiple locations, according to police.

Winnebago County Sheriff Gary Caruana reported that a young woman sustained stab wounds to her hands and face while fleeing from the suspect and is now hospitalized and undergoing intubation. Additionally, another man, described as a “good Samaritan” by Sheriff Caruana, sustained less severe stab wounds while attempting to assist the woman.

Rockford Police Chief Carla Redd noted that not all victims were stabbed, and none suffered gunshot wounds, adding that authorities do not suspect any other individuals to be involved in the incident.

“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 local Ruth Gallagher informed CBS that her longtime mail carrier was among those who had died, a statement corroborated by the US Postal Service, which confirmed the death of a postal worker.

“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.”