Detective Steve Adair said police received multiple calls just after 5 am reporting shots fired at the party attended by more than 50 people. He said by the time officers arrived, the suspect or suspects had already fled.
Police found five people in and around the house with gunshot wounds. Adair said two other people later showed up at hospitals for treatment.
Police said they don't know how many suspects are involved and don't have a motive for the shootings.
Local residents said the gunfire shattered the pre-dawn quiet of the tree-lined neighbourhood.
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"All I heard was like this 'pop, pop, pop, pop.' I was half asleep, half awake, and that's all I heard, and I didn't really know what it was so I just went back to sleep," said Nita Nestman, who lives in a condo on the same street.
Nestman said the street had been quiet for most of the evening. When she heard the noise she didn't expect it to be gunfire.
A black sweater lay on the sidewalk in front of what appeared to be a newly built house. Snow in the front yard was trampled.
A police spokesman called the shooting a "one-off" and suggested there was no danger to others in the city. "That offense took place because the wrong people congregated in that place," he said.