Amir Johnson, 19, was taken into custody on North Robinson Street in West Philly, authorities said in a release.
Johnson was one of three suspects named in the June 24 shooting that injured a 5-year-old boy and his grandfather, city police have said.
A man told investigators he was driving along 61st Street with his 71-year-old father and his young son when the occupants of a white car began shooting at them. The man pulled into a gas station where the shooters followed and continued their assault before fleeing west on Passyunk Avenue, according to police.
The 71-year-old victim was hit in the lower back and hospitalized in critical condition while the 5-year-old was grazed along his shoulder and later listed in stable condition, authorities said at the time.
The suspects' vehicle, a white Kia K5, was found abandoned a few blocks north on 61st Street, police said. It had previously been reported stolen in a robbery at the Philadelphia International Airport.
The other two suspects, Antwan Grimes and Keon Smith, were arrested last July and September respectively, court records show.
Click here to follow Daily Voice Drexel Hill-Upper Darby and receive free news updates.