The estranged boyfriend of a Queens mom who was murdered alongside her son and niece was arrested by officers in Maine Thursday in connection to the triple slaying, police said.

Travis Blake, 29, was picked up by members of the Regional Fugitive Task Force one day after he was named a suspect in the gruesome killings of 55-year-old Karlene Barnett, whom he had been dating, her son Dervon Brightly, 36, and Barnett’s 22-year-old niece, Vashawnna Malcolm.

The three relatives were found dead inside Barnett’s South Jamaica home on June 24, police said.

Two days before authorities discovered the grisly scene, Blake had stopped by Barnett’s house to grab his belongings, sources said.

Malcolm, who had been visiting from the nation of Jamaica, was found gagged and bound with multiple stab wounds in a second-floor bedroom, according to police sources.

The bodies of Barnett and Brightly were found in the basement. Each suffered trauma and stab wounds, police said.

The three had reportedly been dead for days before their bodies — already decomposing in the summer heat — were discovered.

Friends and neighbors were shocked to learn of the triple homicide.

“All of us are trying to fathom how this animal took out three people,” Danielle Richardson, a friend of Brightly, told the Post Sunday.