A Petaluma contractor was found guilty of stealing from elderly clients, whom he bilked for more than $500,000 in excessive charges, according to the Sonoma County District Attorney’s Office.

William Edward Hail III, 44, a licensed plumber, now faces up to seven years in prison. He became the subject of a Petaluma police investigation after a relative of one of his clients reported that they believed he had taken advantage of their 82-year-old family member, prosecutors said.

Hail was hired in 2012 by the Petaluma man to install solar panels and a wind turbine, and to do similar work for an 83-year-old female acquaintance, authorities said.

In the end, each victim paid Hail more than $325,000 for completed work that should have come to no more than $41,000 and $88,000, respectively, according to an industry expert who testified at trial.

A review of Hail’s bank records showed he deposited the money into personal accounts and spent it on vacations, entertainment and restoration of classic automobiles, prosecutors said.

A Sonoma County jury Thursday returned guilty verdicts for two counts of elder theft, two counts of diversion of construction funds and one count of perjury. Sentencing is scheduled for January.

“Elder theft continues to be a significant issue in our community, so we encourage anyone who suspects that an elderly family member or friend may be taken advantage of to contact law enforcement immediately,” District Attorney Jill Ravitch said in a statement.