An eight-year-old boy is in critical condition after being shot at a waterpark in the US state of Michigan. 

Some nine people were shot at a waterpark in Detroit, Michigan, including the eight-year-old boy, his mother and four-year-old brother. 

The eight-year-old and mother are in critical condition, while the younger son is reportedly in stable condition. 

Another six victims, who are all aged 30 or over, including a husband and wife and a 78-year-old man, are said to be in stable condition. 

The shooting began after 5pm local time at the Brooklands Plaza Splash Pad. 

Police tracked the suspected gunman, described as a 42-year-old white man, to a home, where they sent a drone inside to find he had died from a self-inflicted gunshot wound, authorities said. 

Michigan shooting

Police say the attack appears to be random, with the gunman driving up to the park, walking to the water recreation area and firing up to 28 times, stopping multiple times to reload. 

Oakland County Sheriff Mike Bouchard told local media the gunman, who at least one witness said was using two handguns, was "apparently in no rush" and "just calmly walked back to his car". 

He added law enforcement had been on the scene within two minutes of the gunman opening fire. 

He said they were sadly unable to prevent the chaos which saw locals "falling, getting hit, trying to run." 

Mr Bouchard said people are still advised to stay out of the area and anyone who was hiding in nearby parks can go home.