An American man, who often wrote social media posts against US President-elect Donald Trump, killed his wife, ex-partner, and his two sons before turning the gun on himself in the US state of Minnesota, media reports said.

The man was identified as 46-year-old Anthony Nephew.

The shooter, 46-year-old Anthony Nephew, had a “pattern of mental health issues,” Duluth Police Chief Mike Ceynowa was quoted as saying by New York Post.

The police chief made the comments a day after they found five bodies in two houses in the city.

Authorities found Anthony Nephew’s ex-partner Erin Abramson, 47, and their son, Jacob Nephew, 15, dead from apparent gunshot wounds inside their home Thursday afternoon, police told New York Post.

Police even recovered the bodies of Anthony Nephew's 45-year-old wife Kathryn Nephew, and their 7-year-old son Oliver Nephew inside their family home.

They reportedly had gunshot wounds.

Anthony Nephew was also found dead inside the home from a self-inflicted gunshot wound, police told the newspaper.