“Only the rifle was used on the victims, authorities said.”
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http://www.bbc.co.uk/news/world-us-canada-20751617
“Lt Paul Vance from Connecticut State Police Department said the main weapon used was an assault rifle.”
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Neither article you referenced said that “the coroner” stated that all of the victims were killed by the rifle. The BBC article did say Lt Vance said it was the main weapon used. The other article quoted “an authority”.
Where did you read or hear that the coroner stated all victims were killed with the rifle?
Again, what troubles me is the inconsistent reporting in the press about this. The MSM is noted for agenda, but the accuracy of reporting on this has been horrible.
if you wish to parse words then do your own research.