Waterloo Region police say Robert Murphy killed himself and Lorrie Baechler in her home on Brock Street in Kitchener.
Baechler, 40, and Murphy, 44, were found dead on Sunday morning, after neighbours reported hearing gunshots.
"This is a tragic and senseless incident that remains difficult for our community to comprehend," said Police Chief Bryan Larkin in a release Thursday.
"At this time, we want to respect the privacy of the families as they grieve their tremendous loss."
Baechler and Murphy were in a relationship, police said, but they couldn't specify whether or not the pair was in a relationship at the specific time of the incident.
Police won't be releasing the results of the autopsies in the deaths of both Baechler and Murphy, out of respect for the families.
"Because of the sensitivity of this situation we are not providing the specifics of that, other than to say we wanted to make it clear to the community ... that we have one individual responsible for the deaths of both," said police spokesperson Olaf Heinzel.