PHILADELPHIA (AP) — A man already serving a life sentence has been acquitted of murder in the shooting death of an aspiring teacher during an iPod robbery in Philadelphia.

The Philadelphia Inquirer reports the jury found Marcellus Jones not guilty of all charges Wednesday, including murder and conspiracy to commit robbery, in the death of 23-year-old Beau Zabel.

Zabel moved from Austin, Minnesota, to Philadelphia to start work in the public schools a few weeks before he was killed in June 2008 during a street robbery that netted an iPod. Zabel had been walking home after finishing a shift at a Starbucks store.

The 37-year-old Jones is serving life for killing a witness in the case. A murder conviction would have meant a mandatory sentence of life in prison without parole.