Thunder Bay Police have identified 8-year-old Brandi Marie Wingert as the victim of Monday's domestic assault on Donald Street.
Police also distributed a photo of the child as part of a news release Thursday afternoon.
"A post-mortem examination was conducted on the 8-year-old victim. The cause of death is currently a matter between the family and the coroner," it stated.
The release said that Wingert's mother was the victim of an initial attack and went on to explain the sequence of events after a 3 a.m. call to 911.
"A 34-year-old female had been assaulted by her ex-boyfriend," police said. "She had sought assistance from a neighbour. A second 911 call came from an adjoining residence.
"Upon arrival at the scene, patrol officers discovered a critically injured 8-year-old girl."
Police said the mother suffered non-life-threatening injuries and a second child was discovered unharmed in the residence.
A neighbour of the family told CBC on Tuesday that police had been involved when the mother of the children broke up with her boyfriend and kicked him out of the apartment last week. But police said there had been no prior incidents of violence reported to them.
Police said the "38-year-old male believed to be responsible for the assault and murder" was the subject of the standoff later Monday morning on Wharton Road.
The three-hour standoff ended when the male was taken into custody.
"The male was rushed to hospital...due to injuries which were sustained prior to the arrest. The male was pronounced dead a short time later," the release said.
"Neither of the children involved in this tragic incident were related to the 38-year-old ex-boyfriend."
The Special Investigations Unit is still looking into the circumstances of the suspect's death as part of its mandate to investigate all deaths that occur in police custody.
Thunder Bay Police said they cannot release the man's name while that investigation is continuing.