Connor McCowen, a Michigan teenager, has been found guilty of killing his sister's ex-boyfriend and has been sentenced to 20 to 60 years behind bars.



During the trial McCowen, 19, had claimed he stabbed Andrew Singler, 23, in self defense after his sister's claims of abuse prompted the fatal fight between her brother and her boyfriend.



McCowen reportedly broke down in court as the sentence was given on Wednesday. The 19-year-old was found guilty of the second degree murder of 23-year-old Singler.



Singler, a Michigan State University senior, was reportedly stabbed to death at 4am on February 23 of this year at his Meridian Township apartment. He was an aspiring pediatric dentist who was planning to go to graduate school after his May graduation.



According to the Daily Mail, Singler had dated Shay McCowen, McCowen's older sister for two years and during that time the two young men grew close.



Shay McCowen told the court that before her brother and her boyfriend got into an angry text messaging exchange, she had told Conor that Singler had 'broken her ribs.'



The back-and-forth text messaging reportedly continued for 45 minutes before the then 18-year-old McCowen drove to the college student's apartment.



During the trial McCowen told the court that he went to the house only with the intention of talking things out, but the situation became heated and Singler punched him in the face.



McCowen then claimed he had defended himself with a folding knife that he had in the pocket of his sweat pants.