Const. Jennifer Kovach, 26, died March 14 as she responded to a colleague's call for assistance around 12:30 a.m., roughly an hour into her shift.
Police released the findings of their investigation into her death at a news conference, saying they had ruled out driver distraction and mechanical failure.
And though Kovach wasn't wearing her seatbelt as required, it likely wouldn't have saved her life if she had, given the "extreme and severe" nature of the crash, Guelph Police Chief Bryan Larkin said.
She died in hospital after sustaining "significant trauma to her torso and head," he said.
Larkin described how Kovach was travelling at 115 kilometres per hour when her cruiser spun out — just one kilometre per hour shy of the critical curve speed for that stretch of road at the time, or the maximum speed a car can reach without losing traction.
However, the speed limit in the area is 50 km/h, police said.
The Highway Traffic Act allows on-duty officers to speed while responding to calls from colleagues or the public, but how fast they go is left to their discretion, said Guelph police spokesman Const. Michael Gatto.
Kovach initially managed to slow down the cruiser and straighten it, but then hit a patch of ice and spun out again before sliding into the bus's path, Larkin said.
"Speed is the primary factor in this collision," Larkin said in a news conference.
"Const. Kovach possessed the abilities and skills to recover from the initial rotation, however, the roadway condition — wet, combined with the ice — created a significant counter-clockwise rotation followed by a slide that was not recoverable in time prior to impact with the transit bus."
The bus involved in the crash had no passengers at the time and the bus driver had only minor injuries.
Kovach had joined the force four years earlier, fulfilling what relatives have said was her lifelong dream.
Her funeral in late March drew thousands to the Sleeman Centre in Guelph, many of them police officers who praised her devotion to the job they said she considered her calling.
Her parents, Bill and Gloria Kovach, described her as a daredevil who never failed to "live loud," as was her motto, and loved to ride dirt bikes and all-terrain vehicles.
As Kovach's relatives and colleagues continue to grieve, Larkin said the force must do what it can to prevent similar tragedies in the future.
"Obviously there's lessons to be learned from this collision. I do not, as chief, ever want to see another family endure what the Kovachs have had to endure," he said.
Collisions involving cruisers have long been a concern, he said, noting there have been 20 in the city so far this year, compared with 17 for all of 2012.
Many questions remain about what happened that fateful night, including why Kovach wasn't buckled up and whether having a cruiser with all-wheel drive — such as the force's newer models — would have prevented the crash, he said.
In the months since the collision, Larkin said he has emphasized the importance of wearing seatbelts.
At the same time, the chief said he doesn't want Kovach to be remembered for the circumstances of her death, or the questions it raised.
"Her legacy will be how she united the community because she's a homegrown police officer, she volunteered in the community, she did tremendous work."
--by Paola Loriggio in Toronto.