CASTRO VALLEY -- A 62-year-old man told Alameda sheriff's deputies that he shot a projectile into a side window of a Waste Management trash truck on Friday because he was angry at a union lockout.

John Boyle, a Castro Valley resident and retired shop steward with a local trucking company, was arrested after a Waste Management replacement driver noticed a side window of the truck shattering around 10:30 a.m. on Friday.

According to authorities, the driver saw a man shut a house window immediately afterward, which led Alameda sheriff's deputies to the 4100 block of Nichandros Street. Deputies contacted Boyle in front of his residence and brought him to a substation for questioning.

Alameda sheriff's Sgt. J.D. Nelson said it was during an interview with sheriff's investigators that Boyle told them he was involved, and why.

Investigators obtained a search warrant for the property and discovered firearms, a crossbow and a wrist rocket-style slingshot, the sergeant said.

The garbage truck was being driven by a replacement worker because Waste Management of Alameda County on July 2 locked out more than 500 employees following four months of unsuccessful negotiations for a new contract.

The locked-out Alameda County garbage workers expanded their picket lines on Friday to Walnut Creek, Sonora and Stockton.

The picket lines could affect service from the Waste Management truck yard in Walnut Creek, which dispatches trucks that pick up recycling and yard trimmings in Lafayette, Walnut Creek and Danville.