A black teenager has been accused of shaking his girlfriend's six-month-old son to death - and then acting as if nothing had happened

Daquan Davis, 19, was looking after Yusuf E’Miy Stewart-Ali Jr. at the apartment he shared with his girlfriend, Ebony Stewart, in Atlantic City, New Jersey as she worked a night shift. Stewart, 25, called Davis around midnight, and he told her that the baby was fine. But when she returned home shortly before 4 a.m., she found her son unresponsive. She said that, after the grisly discovery, Davis acted as if nothing had happened. Davis was arrested after authorities determined that the baby had been shaken, prosecutors said. Davis, who graduated from high school in June 2012, has been charged with aggravated manslaughter and endangering the welfare of a child. He is held on $750,000 bail. Stewart said that her boyfriend's full name is actually Da'Quon Callaway and he is not the baby's father. She met him a month ago and said that they had been living together at the apartment since.