(CNN) Police are looking for a suspect after seven people were shot at a 2-year-old's birthday party in Camp Springs, Maryland, on Saturday night, authorities said.

Three victims suffered serious injuries, four have less serious injuries and all are expected to survive, Prince George's County Police Chief Hank Stawinski said at a news conference. The victims range in age from 18 to 20 years old.

Stawinski said about a dozen people were gathered for the toddler's party when one person came up and a fight broke out, ending with gunshots.

Police believe this was the act of a single shooter, the chief added.

Camp Springs is a suburb of Washington, DC.