By Ryan Gorman PUBLISHED: 11:20 EST, 24 February 2014 | UPDATED: 13:33 EST, 24 February 2014 A Sunday school teacher who killed another man in a road rage brawl last year faces only one year in jail after an autopsy revealed he died because of a problem with a popular anti-stroke drug. Librado Cena, 58, killed William O’Brien with a single punch to the head last April after the two men fought in a Fairfax City mall parking lot because the 63-year-old honked at him too many times. Cena remarkably faces only 12 months in prison on a misdemeanor assault and battery charge in a trial set to start Monday after initially facing life because an autopsy revealed the unstoppable bleeding – not the punch – caused O’Brien’s death.
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William O'Brien, 63, died after only one punch to the head from 58-year-old Librado Cena
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Cena initially faced life in prison, but now stands charged only with misdemeanor assault
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Doctors attributed O'Brien's death to a blood thinner causing unabated bleeding on his brain after the punch
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Misdemeanor assault carries a maximum prison sentence of only one year
@placeholder lost his job as the religious director of the local church, his wife told the paper.