Since Sunday, eight shootings have occurred in the city, The Detroit News reported.
In Thursday's incident, three men, ages 19, 20 and 22, were sitting in a car about 6 a.m. when an individual approached and opened fire.
Two of the men were listed in serious condition and the third was in stable condition.
Two men were shot and killed inside vehicles in separate incidents Tuesday and Wednesday.
The man killed Wednesday was sitting inside an SUV with two women about 4 a.m. when he was shot during an attempted robbery. The man died as the women rushed him to an emergency care facility.
In Tuesday night's shooting, a 54-year-old man died after someone pulled up in a Jeep and shot him as he sat in his car.