Officers went to a home inside a gated community located in the 50 block of Riverboat at about 10:30 a.m., intending to conduct a welfare check, according to the Irvine Police Department.
"Extended family members of the residents of the home reported to Canadian authorities they had been unable to reach the residents for over one year and were concerned," after which the Canadian officials contacted Irvine police, the department said in news release.
A father, mother and adult son reportedly lived at the residence, according to the statement. When the officers entered the home, they discovered three "severely decomposed" bodies that appeared to be adults.
According to investigators, there were no signs of forced entry into the home and no suspects are being sought in the case. A gun was recovered inside the home.
"There are some indications this was a domestic related incident that resulted in a murder-suicide," the police statement said, without providing additional details.
Police say they believe the three bodies may have been there for up to 18 months and are investigating how the case went unreported for that long.
"As I understand it, there's a homeowners' association that's responsible for at least some of the lawn care and maintenance for the front of the homes," Irvine police Lt. Bill Bingham said. "Looking at the home at a glance it's not immediately apparent that somebody hasn't been in and out of the home for maybe up to a year."