The incident happened at approximately 11:45 a.m. in the 1700-block of West Erie.
The gunman has been identified as Arturo Bahena. The victims are 42-year-old Rodolfo Bahena and 44-year-old Romeo Bahena.
Family members were distraught to arrive at the scene and learn what happened.
Neighbors say the relatives had been arguing about selling the house, but they never saw signs of that type of violence.
"He looked stable. He looked nice and clean. He looks clean. He looks normal. Just, I know they have a difference with the house," said neighbor Eloisa Morena.
The alleged gunman and one of the victims were pronounced dead at the scene. The third victim died a short time later at Northwestern Memorial hospital.
