Rivera and 27 year old Viameri Santana-Berrious were both wanted for the death of 9-month old Milton Galarza-Rojas.
Medics responding to a 911 call around 2:30am in the 4500 block of North 7th Street found the baby non-responsive and rushed him to St. Christopher's Hospital where he was pronounced dead just after 3:00am.
The medical examiner has determined the cause of death was from heroin and cocaine intoxication.
Both Rivera and Santana-Berrious face homicide charges.
Rivera was taken into custody late Friday night. Police are still searching for Santana-Berrious.
Anyone with information is asked to contact the Philadelphia Police Homicide Unit at 215-686-3334, 215-686-3335, 215-686-3336 or 911.
