OAKLAND — An FBI agent who left a firearm in an unattended car where it was stolen back in July won’t have to pay a fine under a state law requiring law enforcement weapons be locked away when left in vehicles.

The reason? The stolen weapon was an AR-15 assault rifle. The state law covers only handguns.

“This is not an infraction we are going to charge,” Teresa Drenick, a spokeswoman for Alameda County District Attorney Nancy O’Malley, said late Wednesday afternoon. Oakland Police cited the agent, identified in court documents as Chris Brown, under a 2016 law sponsored by state Sen. Jerry Hill, D-San Mateo.

But while the agent won’t be fined up to $1,000, four men are facing criminal charges in the theft and sale of the weapon, a Colt Ar-15 M-4 assault rifle, court documents show. The weapon was eventually recovered.

Malik Jones, 22, of Daly City, Deon Norton, 21, of San Francisco, and Jake Burns, no age or address given, face five felony counts each associated with the theft and sale of the weapon. Parker Prowell, 21, of Santa Cruz, the person who allegedly bought the rifle for $1,500, was also charged, according to court records.

Records show Norton allegedly broke into Brown’s locked 2018 Dodge Durango, described as a “covert surveillance vehicle,” on July 10, and took the rifle, two clips of hand-gun ammunition and an FBI jacket. Jones and Burns allegedly were accomplices.

According to court records, prosecutors allege that Norton and Jones each received $750 in the sale, and Burns took a $100 finder’s fee for leading Norton and Jones to Prowell in Santa Cruz.

All four men pleaded not guilty to felonies in Alameda County Superior Court last month.

Prowell was released without charges when police first questioned him, records show. But surveillance footage later show all four defendants walking around Norton’s vehicle at an undisclosed location. A bag was exchanged Norton and Jones were seen counting “what appears to be a large amount of cash outside Norton’s vehicle,” according to a probable cause declaration by Oakland Police Officer Kevin Godchaux.

Burns later “confessed to his role in” the theft after being arrested in Hawaii, according to the declaration.

A retired FBI agent told this news organization last month that the agency has strict policies about the storage of weapons in vehicles and that the agent involved would likely face discipline in the matter.

This news organization reported in 2016 — a year after Kate Steinle of San Francisco was shot and killed with a gun stolen from the parked vehicle of a U.S. Bureau of Land Management ranger — that at least 944 guns were either stolen from cops working in the Bay Area since 2012, or agencies had lost them.

Juan Francisco Lopez-Sanchez, an undocumented immigrant who also goes by the name José Inez García Zárate, was charged with murder in state court but later acquitted. He still faces federal gun charges.

The citation issued to Brown for not properly storing the weapon was one of the first known uses of the 2016 law. A spokeswoman for Hill said his office has no information on how many times the law has been applied. The spokeswoman also said Hill faced stiff opposition to including long guns in his legislation.

Drenick, a spokeswoman for the Alameda District Attorney, said the office sponsored legislation last year meant to close a number of loopholes and shortfalls in criminal law. It included an attempt to require long-gun storage in law enforcement vehicles.

The bill didn’t pass.

Staff writer George Kelly contributed to this report.