A gunman shot three people, killing two and injuring one, before taking his own life on Saturday at an apartment building in Brown Deer, Wis., a village north of Milwaukee, the police said.Peter A. Nimmer, the police chief of Brown Deer, said that what started as a domestic dispute between two people escalated into gunfire.Chief Nimmer said that the police were unsure where the dispute started, but knew that it unfolded in the building’s parking lot, hallway and second floor.“Right now we are unsure of the relationship of all the victims involved, but we know at least two knew each other,” Chief Nimmer said. The identities of the victims were not made public, but the authorities said it was a man and a woman.A child was in the gunman’s apartment but was unharmed and placed with relatives, he added.Officers were dispatched to the building, the Park Plaza Apartments, at 10:09 a.m. in response to reports of a shooting and were fired upon from the second floor when they arrived, Chief Nimmer said.He said that officers did not return fire. A patrol vehicle was struck, but no officers were hurt, he said.After the gunman fired on the police, officers heard a gunshot that they believe was the gunman taking his own life. Officers took the gunman, whose name was not made public, to the hospital, but he did not survive.The police did not offer a motive for the attack.The police said they had “no reason to believe that there is any danger to the community at this time.”The F.B.I. and the Milwaukee County Sheriff’s Office helped with the response, which drew a heavy police presence, including two armored vehicles.