(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.

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