On Earth Day this spring, 30,000 dead fish washed up on the banks of Cleveland’s Rocky River. Biologists and wildlife crews were initially baffled by the source of the disaster, but officials have since identified cyanide as the source of the fish kill.

On Wednesday officials accused Grafton, Ohio residents Renato Montorsi, 79, and his wife Teresina, 74, of pouring 55 gallons of the poisonous liquid down a storm sewer. A grand jury indicted the couple on charges of conspiracy and obstruction of justice, and Renato Montorsi is accused of Clean Water Act violations, reports

Former owners of a metal-plating company that used cyanide, the Montorsis now own a coin and precious metal business in the same spot. U.S. Attorney Steven Dettelbach said trash collectors wouldn’t accept a barrel of cyanide from Renato Montorsi, so Montorsi violated environmental disposal regulations and dumped the poison.

As a direct result, nearly all the fish and water-dwelling wildlife were killed along a three-mile stretch of the Rocky River’s East Branch. Thousands of the dead fish were game fish, and included species like rainbow trout, steelhead trout, and smallmouth bass.

The Montorsis have not been arrested, but will soon be summoned to federal court to answer for their actions.