A traffic stop around 12:05 p.m. Sunday on eastbound I-580 at 150th Avenue in San Leandro led to a probable cause search that yielded a fully loaded AR-15, police said.
The AR-15, which had 50-round drum machine with one bullet in the chamber, was found concealed in a bag in the vehicle's backseat, San Leandro police said.
Police also recovered an "It" clown mask and marijuana from the vehicle. The suspect was arrested, transported to jail and booked on multiple drug and weapons violations, officials said.
"This was a great traffic stop that took an illegal and dangerous weapon off the street," San Leandro police wrote on Twitter. "This is another positive outcome in keeping the citizens of San Leandro safe."