A 24-year-old man has been convicted of all counts on charges he brutally attacked his girlfriend's twin 2-year-old daughters, killing one of them and leaving the other critically injured with a lacerated liver and internal bleeding. 

A jury found Derran Morris, of Mount Vernon, guilty of second-degree murder and first-degree manslaughter, both felonies, in the death of Addison Turner. He also was found guilty of first- and second-degree assault in the beating of her twin sister, Annalynn.

Morris and the twins' mother, Monique Turner, walked into a Westchester County emergency room shortly after 5 p.m. on July 5, 2017 carrying Addison and her twin sister in their arms, prosecutors have said. They told reception that Addison wasn't breathing. Hospital workers found Addison had no pulse and was cold to the touch. Doctors and nurses worked for 20 minutes to try to revive her. 

Annalynn was taken to a different hospital, where doctors found she had life-threatening abdominal trauma, including a lacerated liver and severe internal bleeding. An autopsy on Addison found multiple bruises, trauma and a long, deep laceration to her liver as well that caused extensive blood loss. 

The medical examiner determined Addison's cause of death to be blunt force trauma and ruled the case a homicide. An investigation found Morris had been alone with the twins for several hours, and he repeatedly struck both of them in the stomach at some point during that time, according to a criminal complaint.

Morris was arrested two days after Addison died. Her sister ultimately survived but required weeks of hospitalization.