Memphis police have charged Michael Foster in the April 2012 death of his 2-year-old step-son, Memphis police said.

Sean Lambert died at Le Bonheur Children's Hospital from blunt force trauma that had caused his internal organs to hemorrhage.

Foster, who was charged with first degree murder and aggravated child abuse, admitted to police was responsible for the toddler's injuries.

Investigators said the 24-year-old called 9-1-1, saying he had found the boy unresponsive in bed. He later told officers he was swinging the boy in a circle while playing with him and fell onto him.

He is held at the Shelby County Jail.