A 911 call was made about 10:40 p.m. from the 600-block of 40th Place, but all that could be heard was unintelligible screaming, Kenosha police said.
When officers arrived, they found three dead inside a home on the block and two with critical injuries.
The two who survived were critically wounded, and one was flown via helicopter to a hospital. The other was taken to a local hospital.
"As a community, we are shocked and saddened by this senseless loss of life," Kenosha Mayor John Antaramian said. "This year we have had 12 homicides and two-thirds of the cases have been results of domestic violence. The current hardships people are facing - including the pandemic - seems to have escalated conflict in some households. If you know someone in crisis, please consider sharing community resources to find them the help they need."
Kenosha police said the shooting appeared to be domestic-related, and they believed the person responsible was among those dead inside the house.
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The surviving victims are a 35-year-old woman and a 14-year-old boy. Those killed included an 18-year-old woman and 17-year-old boy. The suspect was a 24-year-old man, police said.
"A tragedy like this is beyond comprehension" Kenosha Police Chief Eric Larsen said.
Neighbors said the incident was very strange for the area.
"A great neighborhood, we don't have problems like this, terrifying, sad, obviously," neighbor Laura Fenn-White said. "I'm sad for the people that lost loved ones more than anything."
Investigators remained on the scene Wednesday.
Resources for those in need
Those struggling with mental illness or other stress-related conditions can call a Crisis Hotline at 262-657-7188, Kenosha police said. Women and Children's Horizons offers help for those dealing with domestic violence and can be reached at 262-652-9900.
If you feel suicidal or you're worried about someone you know, you can call the National Suicide Prevention Lifeline at 1-800-273-8255. You can also text the Crisis Text Line by messaging TALK to 741741.
For more information, visit suicidepreventionlifeline.org.