At least four persons have been confirmed dead after a 22-year-old U.S. citizen on Wednesday embarked on a stabbing spree that left his childhood friend, mailman and a female teenager dead and seven others critically injured in Rockford, Illinois.

Christian Soto, 22, admitted to killing the four with a knife while claiming to have been under the influence of marijuana and an unknown substance during interrogation with the police.

Jenna Newcomb, 15, Jacob Schupbach, 23, Jay Larson, 49 and 63-year-old Romona Schupbach were identified as victims of the suspect’s rampage that lasted 20 minutes on Wednesday.

Mr Soto has already been charged with first degree murder, home invasion and seven counts of attempted first-degree murder, and he was expected to appear in court on Thursday.

The police had yet to determine a motive for the multiple deaths caused by Mr Soto but investigations were still ongoing.

District Attorney J. Hanley of Winnebago County said more charges would surface as the case was being unraveled by police detectives. According to Hanley, the suspect bludgeoned three victims with a baseball bat which caused Ms Jenna’s death. 

The mayor of Rockford, Tom McNamara, described the incident as shocking but stressed that his “primary concern is ensuring that our community members directly impacted by this violence are supported throughout their healing and recovery,” CBS cited him as saying.

The mayor announced that free counselling sessions will be provided to residents to help them deal with the trauma of the incident.

“We are working with community partners to provide support and services quickly and conveniently to those residents. We will announce those details soon.”