The killings happened about 10:30 p.m. Wednesday, The Detroit News reported. The mothers of the girls, an infant and a 5-year-old, and a male acquaintance were shot in front of the girls.
Police initially received the wrong address in a report of the shooting, so the bodies weren't discovered until Thursday.
Detroit Police Officer Cassandra Lewis said the bodies were unidentified as of Thursday.
"They all appear to be in their mid-20's," Lewis said.
Police confirmed Friday that a suspect in the case had been arrested but no other details were reported.