Police said in a Monday news conference that they believe the attack was premeditated and isolated, CNN reported.
"The victim suffered massive trauma that was both life-threatening and life-altering," Division Superintendent Heather Ramore said in the press conference. "The attack was meant to end the victim's life."
Ramore said the crossbow the man used is "commonly used by hunters to kill large game, such as moose and deer."
Police have released surveillance video showing part of the incident. They’re asking for the public’s help in identifying the man, whose face can be seen in the video.
The victim spent several months in the hospital and will be in a "recovery phase for the rest of her life," said Peel Regional Police Detective Sgt. Jim Kettles.