Janesville police believe a dispute over a relationship with a Madison woman led to a murder-suicide on the city’s south side Thursday night.

Deputy Chief Todd Kleisner said a 43-year-old Madison man came to Janesville to confront a 27-year-old Janesville man, who he shot and killed before taking his own life.

The 43-year-old man had a child and lived with a 28-year-old Madison woman, who was in Janesville Thursday night visiting the 27-year-old man who she had a previous relationship with.

Police did not identify either man or the woman because they are all considered victims in the incident and protected by Marcy’s Law.

The 43-year-old and 27-year-old were both co-workers at B & G Foods in Stoughton. When the 43-year-old man went to work Thursday night, he discovered the 27-year-old man was not at work and determined he was instead in Janesville with the 28-year-old woman in the 1100 block of Kellogg Avenue.

Investigators believe the shooter fired at least nine shots, and no other trailers or victims were affected by the shooting. The 28-year-old woman was present at the time but uninjured in the gunfire.