ROCKFORD, Ill. -- Four people, including two young boys, were killed in a shooting late Saturday at a home in the northern Illinois city of Rockford, authorities said.

Police said a 24-year-old woman, her boyfriend and her two sons were found dead of gunshot wounds around 11:20 p.m. Saturday inside a red-brick duplex in Rockford, the Rockford Register Star reported. Authorities identified the victims as Martia Flint, 24-year-old Demontae Rhodes, 6-year-old Tyrone Smith III and 4-year-old Tobias K. Smith.

Assistant Deputy Chief Patrick Hoey said neighbours reported hearing pounding on a door and someone forcing the door open before hearing gunshots. He said police have no known motive.

The victims were pronounced dead by Rockford Fire Department paramedics after being found inside the home.

Autopsies were scheduled for Monday, according to Winnebago County Chief Deputy Coroner William Hintz.

The deaths brought the number of homicides in Rockford to 17 in 2014, according to the newspaper's database. There were 22 homicides in Rockford last year and 14 in 2012.