Ladell Willis, 20, of Vallejo, was allegedly one of two suspects who grabbed a woman and tore a necklace from her in the 4700 block of Business Center Drive in Cordelia around 2:30 p.m. on May 3, police Sgt. Rob Lenke said.
Witnesses gave police a description of the suspects and the waiting vehicle in which they fled, Lenke said.
Detectives served a search warrant at a Vallejo residence Thursday and arrested Willis, the primary suspect, for robbery, being a felon in possession of a firearm and possessing an unregistered firearm, Lenke said.
Police also recovered a handgun in the Vallejo residence, Lenke said.
"This is anther example of citizens taking an active role in the safety of their community by being good witnesses and providing critical information to the Police Department," Lenke said.