
She told investigators she didn't know she hit him.
A Boston police officer found buried in the snow was run over and killed by his girlfriend, investigators believe.
The body of Officer John O'Keefe, a 16-year veteran of the force, was discovered lying outside a Canton home on Saturday morning during a heavy snowstorm.
He had suffered a serious head injury; the District Attorney later said he'd been left in the cold for some period of time.

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View StoryOn Tuesday night, police arrested 41-year-old Mansfield woman Karen Read, whom multiple sources identified as his girlfriend.
She was charged with manslaughter, leaving the scene of a motor vehicle collision causing death and motor vehicle homicide.
Investigators say they have Ring Cam footage of the incident. According to prosecutors, O'Keefe knew the owners of the home where he was found, about two miles from where he lived; NBC10 Boston reported that property records show the homeowner has the exact same name and middle initial as a veteran police sergeant, though the Boston PD would not confirm it.
At Read's arraignment on Wednesday, prosecutors said the couple went to at least two bars together before driving to the home on Fairview Road around midnight; Read said she left O'Keefe there and went home because she was not feeling well. She said she made a three-point turn and left, but did not see O'Keefe enter the house.
She told investigators that she later tried to contact him, but couldn't get hold of him; the next morning, she said she noticed her tail light was broken.
She returned to the Fairview Road home hours later with a friend, and was heard saying "Could I have hit him? Did I hit him?" prosecutors said, per WCVB.
After finding him in the snow with severe cuts on his arm and head, eyes swollen shut and bleeding from the nose and mouth, they called 911, CBS Boston reported. The court heard that Read thought he might have been hit by a snow plow.

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View StoryThe medical examiner later determined O'Keefe suffered multiple skull fractures and hypothermia.
Arguing for $5,000 bail, Read's defense attorney said she suffers from a myriad of health issues, including colitis and multiple sclerosis, and had been diagnosed with a brain tumor last summer.
However the judge said she had "plenty of reason to flee" and ordered she be held on $50k bail, and to have no contact with the victim's family. She was subsequently released on that bail amount.
Among those O'Keefe leaves behind are the niece and nephew he adopted and raised, after his sister died of cancer and her husband shortly after that.
"The Boston Police Department continues to grieve over the tragic loss of our brother Police Officer John O'Keefe," Superintendent-in-Chief Gregory Long said in a statement.
"John was a kind person, dedicated to his family, and will be greatly missed by his coworkers and anyone who had the privilege of meeting him."
A Boston PD spokesperson told NBC10 that no internal affairs cases have been opened in connection, and no one has been placed on administrative leave.
