A father-daughter couple who allegedly had an incestuous relationship were found dead in an apparent murder-suicide along with their love child, according to police.

Steven Walter Pladl killed his daughter, Katie Rose Pladl, their baby boy and Katie’s adoptive dad in a multi-state shooting spree Thursday before ultimately turning the gun on himself, news station WTVR reported.

The triple murder-suicide came after the biological dad and daughter were arrested in January on incest charges following the birth of their son.

Authorities said the murderous rampage started in Knightdale, NC, where the 45-year-old man killed their 7-month-old son. The baby, Bennett Pladl, was discovered dead Thursday morning by officers responding to a welfare check.

Steven then went to New Milford, Conn., and allegedly shot his 20-year-old daughter and her 56-year-old adoptive father, Anthony Fusco, to death. They were found dead Thursday morning inside a truck with the window shot out at an intersection on Route 7, news station WTIC reported.

Police later discovered Steven dead of an apparent suicide just miles away, across the state line in Dover, NY, according to WTIC.

The couple was set to appear in court April 23.

Authorities said the father and daughter, who allegedly planned to wed, were living as a couple in North Carolina. They were arrested after officials were notified about a possible love child.

Steven and his ex-wife gave Katie up for adoption in 1998. The biological parents reportedly reunited with their long-lost daughter in 2016 after she tracked them down on social media.

Soon after, Steven and Katie began a sexual relationship, giving birth to a child in September 2017, according to reports.