(CNN)A man was arrested after he called 911 and said "his family was dead," Milwaukee Police Chief Alfonso Morales said.
Officers responded to the home after receiving a call around 10:30 a.m. Monday, Morales said at a press conference. They discovered four teenagers and an adult dead.
The victims were all known to the man who called, according to Morales. "This is a very tragic event."
Authorities on Tuesday identified them as Demetrius R. Thomas, 14; Tera R. Agee, 16; Lakeitha M. Stokes, 17; Marcus G. Stokes, 19; and Teresa R. Thomas, 41.
A weapon was recovered at the scene and it is believed that the shooter acted alone, the chief said.
A child, believed to be 3 years old, survived the shooting, according to Mayor Tom Barrett, who spoke with CNN affiliate WDJT when he visited the scene.
A 43-year-old man remains in custody and the case will be presented to the district attorney's office in the coming days, Morales said.
It is unclear what led to the shooting.