PHILADELPHIA — A convicted killer already serving a life sentence has been charged in the shooting death of an aspiring teacher gunned down for his iPod a month after moving to Philadelphia.

Beau Zabel moved from Austin to Philadelphia in May 2008 and was scheduled to start work in Philadelphia public schools. The 23-year-old man was shot dead a month later in a robbery.

Marcellus Jones was charged Wednesday in the murder. He is already serving a life sentence for killing his get-away driver in the Zabel killing.

Authorities said last month that charges were imminent. They said a witness stepped forward to tell police that Jones displayed the iPod and claimed he killed Zabel after realizing it wasn’t a more valuable iPhone.