A Union Bank lies in ruin after it was set ablaze the night before by arsonists and looters in downtown La Mesa. Photo by Chris Stone

Two men were behind bars Tuesday on suspicion of torching buildings and looting businesses during a La Mesa police-brutality protest that devolved into rioting and violence last spring.

Ricky Bernard Cooper, 33, and 19-year-old Alexander Jacob King were arrested Monday for their alleged roles in the destructive demonstration in the East County city, according to the FBI.

Both suspects are expected to face charges of arson and burglary, the federal agency reported. Cooper also was booked on a vandalism charge, according to jail records.

Cooper and King allegedly committed the crimes during a May 30 protest prompted by violent police encounters with Black men — the Memorial Day in- custody death of George Floyd of Minneapolis and the arrest two days later of 23-year-old Amaurie Johnson of San Diego at Grossmont Transit Center in La Mesa.

According to jail records, King is White with blond hair and hazel eyes, standing 6 feet tall and weighing 160 pounds. He’s being kept at San Diego Central Jail.

Cooper is Black with green eyes, standing 5-10 and weighing 180 pounds, the records show. He’s also being held at the downtown jail.

As the initially peaceful afternoon demonstration erupted into chaotic unrest, a crowd estimated to number as high as 1,000 blocked nearby Interstate 8 in both directions for a time.

Footage from the scene showed at least one vehicle ablaze near La Mesa City Hall and vandals smashing storefront windows at a nearby shopping center.

After nightfall, looters and arsonists burglarized a closed Vons supermarket, a Sprouts store and a Goodwill retail outlet; smashed windows at other businesses; and set two banks ablaze.

The arrests of Cooper and King stemmed from a joint investigation by La Mesa and San Diego police and the FBI, according to the federal agency, which did not disclose what led authorities to identify the two men as suspects in the case.

— City News Service contributed to this report.