Six people were killed in the US state of Iowa after a series of shootings that appeared to stem from a domestic dispute, police said.

The suspected shooter also was found dead with a self-inflicted gunshot wound, according to the Muscatine Police Department.

The victims are believed to be family members of the suspect, identified as Ryan Willis McFarland, 52, of Muscatine, the department said.

Muscatine Police Chief Anthony Kies called the shooting an "act of evil".

The shootings took place on Monday at multiple locations within the city of Muscatine.

Police received a report of a shooting just after noon on Monday. When officers responded to a home, they found four people with gunshot wounds, police said.

All four victims were pronounced dead at the scene.

McFarland had left the residence before officers arrived, but officials found him shortly after on a riverfront trail near a pedestrian bridge.

He had a self‑inflicted gunshot wound, police said, and received medical aid, but was pronounced dead at the scene.

Detectives later found another man dead from an apparent gunshot wound in a different residence. A further search led officers to a business, where they found another victim, also dead of an apparent gunshot wound.

Online maps show a metal workshop at the address provided by police.

"Preliminary findings indicate the shootings stemmed from a domestic‑related dispute," McFarland police said in a statement. "All victims are believed to be family members of the deceased suspect."

Kies did not give the names or ages of the victims and noted that the investigation is ongoing.

He confirmed the suspect had an existing criminal record but did not share any further details.

Muscatine, in south-east Iowa, sits on the Mississippi River and has a population of approximately 23,500 people, according to US government data published last year.

Mayor Brad Bark wrote in a post on Facebook: "Our hearts are heavy tonight after the tragic shootings that claimed innocent lives."