A person who knew the victims called 911 around 10:15 a.m. after they found them stabbed to death, the Middlesex District Attorney's Office said. There were signs that someone had forced their way inside the home.
Police are still working to identify the victims.
Broadway Street between Churchill and Linwood Avenue remained closed Sunday night as investigators continued to process the crime scene, prosecutors said just after 10 p.m.
There was an attempted break-in at Brookside Avenue, about a half-mile from the murder scene, that took place on Sunday morning, the prosecutor said. Investigators do not know if they are connected.
Police are asking residents of Nonantum and Newtonville neighborhoods to check their home security videos and report anything suspicious to police immediately.
Newton police have increased patrols in those neighborhoods as the investigation continues.
Authorities ask anyone in that area to remain vigilant, lock their doors and windows, and immediately report anything suspicious to Newton Police at 617-796-2123 or 911 if it appears to be an emergency.
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