A former Sacramento County sheriff's deputy has pleaded guilty to a federal charge stemming from the illegal sale of dozens of weapons, some of which were used by criminals.

Prosecutors in Sacramento say Thomas Lu and fellow former deputy Ryan McGowan, both of Elk Grove, bought and sold handguns that cannot be legally owned by citizens in California.

Lu, age 42, pleaded guilty Tuesday in federal court to one count of dealing in firearms without a license, which carries a maximum sentence of five years in prison.

He is agreeing to cooperate with investigators as part of a deal that could bring him a lighter sentence.

The deputies are charged with serving as straw buyers who trafficked in restricted handguns.