A Douglas County judge Friday sentenced a 19-year-old Lawrence man to serve nearly five years in prison for using a BB gun to rob a Walmart store last December.

District Judge Michael Malone sentenced William O. Paterson to 59 months in prison for his role in the Dec. 13 robbery at Walmart, 3300 Iowa. Paterson in June pleaded guilty to aggravated robbery, conspiracy to commit aggravated robbery and conspiracy to commit aggravated arson. He admitted to using a plastic BB gun to scare away clerks and grab cash from a register at Walmart’s money center, but Kathleen Britton, an assistant district attorney, said victims believed Paterson had a real gun.

The judge followed a plea agreement from attorneys for Paterson to serve sentences for the three convictions concurrently or at once. He also could qualify to get credit for 15 percent off his sentence through good behavior.

Prosecutors also accuse Lonnie S. Schaefer, 22, of orchestrating the Dec. 13 robbery. Paterson told Malone he had suggested conspirators throw a bottle of gasoline on the roof of a building across town to create a diversion. Prosecutors have said co-defendants threw the object at McDonald’s, 1309 W. Sixth St., but damage to the roof was minor. Schaefer’s case is still pending, and four other people are accused of serving as lookouts.

Defense attorney John Ambrosio said Friday that Paterson’s family members, who live in Washington, D.C., and France, were puzzled by the case because Paterson had no past criminal history.

“I am satisfied that this is going to be a life-learning lesson for you, and that’s an understatement,” Malone said.