LYNN – A Baker Street teenager who admitted to shaking his girlfriend’s 2-month-old daughter will be arraigned next week in District Court on a murder charge following the infant’s death Thursday at Massachusetts General Hospital.Prosecutors earlier this week said Alonzo Guzman, 18, 30 Baker St. #2, admitted to shaking Lizbeth Guzman last Saturday night. At his April 27 arraignment, Guzman, who is not the baby’s father, pleaded innocent to assault and battery with serious injury on a child. During the arraignment, Assistant District Attorney Jennifer Kirshenbaum said the child’s chances of recovery were “grim.”Police reports indicate Guzman initially told officers he was changing the girl’s diaper and turned away from her to prepare a bottle for her feeding. When he turned back “she appeared to have trouble breathing.”He told officers he tried rubbing her torso to stimulate breathing and sought help from a downstairs neighbor after about five minutes.MGH Dr. Danielle Dwyer told police Sunday the child had sustained a head injury and investigators subsequently questioned Guzman who told them sometime during the previous week he was “holding the baby and she fell on her face.””He admitted to shaking (Lizbeth). He said he moved her and he lost control,” Officer Joseph Chadbourne stated in his report, quoting Guzman.An MGH doctor told police the child’s head trauma “was consistent with a non-accidental injury.”