The man responsible for more than two dozen heroin overdoses — which all occurred in one day in a state deemed the ground zero for the opioid epidemic — faces up to 20 years in federal prison.

Bruce Lamar Griggs, 22, pleaded guilty on Monday to distribution of heroin, about six months after 26 people overdosed in Huntington, a city in the southwest corner of West Virginia. The 911 calls came within hours of one another, the majority of which concerned overdoses in and around one apartment complex.

Federal prosecutors say Griggs, known as “Benz” or “Ben,” admitted supplying heroin to all 26 people, who overdosed immediately after taking the drugs. Laboratory tests of blood and urine samples showed traces not only of heroin, but also of fentanyl and carfentanil — synthetic opioids that are exponentially more powerful than heroin or morphine.

Fentanyl, meant to treat severe pain, is 50 to 100 times as potent as morphine, according to the Centers for Disease Control and Prevention. The drug is often mixed with heroin or cocaine, unknown to users.

Carfentanil, used for tranquilizing elephants and other large mammals, is 10,000 times as strong as morphine, according to the Drug Enforcement Administration. Last year, the federal agency warned that illegal use of carfentanil is becoming more common and has been linked to a significant number of overdose deaths in the country.

Matt Boggs, executive director of Recovery Point of Huntington, said the torrent of 911 calls Aug. 15 deeply alarmed a community already ravaged by the opioid epidemic.

“To have such a significant amount of overdoses in one day is indicative that the substance that's being sold is containing something very, very poisonous,” Boggs told The Washington Post. “It was definitely alarming, and it really put the community in a state of disbelief, a state of terror, almost.”

No one died as a result of the overdoses.

West Virginia has the highest rate of overdose deaths in the country.

In 2014, 627 drug-related deaths — or 36 for every 100,000 people — were reported in the state, according to the CDC. In 2015, that number went up by nearly a hundred, to 725 deaths — or 42 for every 100,000 people.

In Huntington, a small city of about 49,000 people, deaths from drug overdoses are nearly 10 times the national average. About 8,000 residents — roughly 16 percent of its population — are addicted to drugs, most of which are opioids, according to the Pew Charitable Trusts.

In December, President Obama signed the 21st Century Cures Act, a law that will provide $1 billion to states for research-based opioid addiction treatment.

Griggs, of Akron, Ohio, will be sentenced in April.