The Petaluma teen was robbed at gunpoint by a male with a handgun outside his home in the 400 block of Marylyn Circle around 8:55 p.m.
The suspect wore a bandana over his face and fled in a gray four-door sedan, Petaluma police Sgt. Tim Lyons said. The teen was not injured.
Petaluma police followed leads and contacted a 16-year-old Rohnert Park boy on Friday. The teen admitted to the robbery and was arrested and booked into juvenile hall for possession of stolen property, robbery and conspiracy, Lyons said.
Rohnert Park Department of Public Safety officers then contacted Petaluma police Friday night about other possible suspects in the robbery of the trading cards and other items valued at $5,000, Lyons said.
Petaluma police went to Baseball Cards and Memorabilia store at 5681 Redwood Drive in Rohnert Park. Rohnert Park police said Javier Zamudio-Saenz, 19, of Cotati, and two other juveniles were attempting to sell some of the stolen property to the store, Lyons said.
Petaluma police found a majority of the stolen trading cards and property in the vehicle Zamudio-Saenz drove to the store, Lyons said.
Zamudio-Saenz was arrested on suspicion of robbery and possession of stolen property and booked into the Sonoma County jail.
Petaluma police are trying to find the weapon used in the robbery and any other possible suspects, Lyons said.
Police are asking anyone with information to call Petaluma police Detective Joel Stemmer at (707) 778-4532.