The actor Brad Renfro, whose career started off well with a part as a young boy in “The Client,” but quickly waned due to his struggles with alcohol and drugs, was discovered dead at his home on Tuesday. He was 25.

“Renfro had injection marks on his hands when he was found dead Jan. 15 at his Wilshire-area home, said Craig Harvey, the Los Angeles County coroner’s spokesman. The cause of death was “acute heroin / morphine intoxication,” and the drugs were injected, Harvey said.

“The final manner of death has been ruled an accident,” he said.

Renfro had insisted he was sober over the phone just before he passed away. The young actor said as much to director, Larry Clark. Renfro had just been offered the main role in “Bully,” a real story about a group of marijuana-smoking Florida teens who kill the neighborhood bully. Clark, one of America’s best chroniclers of teenage desperation, had just cast Renfro.

Clark eventually met his 18-year-old star, however.

On his way to the film’s Florida setting, the filmmaker, who had formerly struggled with heroin addiction, went by Renfro’s Knoxville, Tennessee, house. Renfro came out of the home he and his grandmother lived in the summer of 2000 with blood running down his arms. He looked 35 and was bloated. And thus began one of the most agonizing downhill spirals Hollywood has recently seen.

“I said, ‘What the (hell) are you doing?’ ” recalls Clark. “He’d been banging coke. He has tracks running down both arms. He looks horrible. I just saw the whole movie going down the drain.” (Financing was contingent on Renfro’s participation.)

Renfro joined Clark for the next three days. They conversed. The young actor often sobbed while continuing to use cocaine. To get him clean for production, Clark came up with a strategy.

“I kidnapped him,” says the director. The pair jumped in the car one day, on the director’s pretense of going somewhere, and Clark just “gunned it” for Florida. “He kicked in the car. He had a seizure. There’s nothing you can do. It doesn’t last that long.”

Renfro was given a trainer and a minder in Florida by the production. Renfro went to 12-step gatherings with Clark. Even so, Renfro would get wine in the nights.

Clark adds, “I’ve been around a lot of addicts and alcoholics, and I remember thinking at the time, this is one of the worst cases I’ve ever seen.”

Renfro was on probation at the time of his death for an arrest on Dec. 22, 2005, as part of an LAPD operation on skid row in downtown Los Angeles. He was one of 14 people who bought fake heroin balloons from undercover officers.

On the sweep, a Times reporter and photographer were there, and a picture of him being taken was used on the first page of the newspaper. He admitted to taking methadone and heroin to the investigator who detained him.

He had been detained several times from the age of 15, and was even found guilty of stealing a boat in Fort Lauderdale, Florida.

He became more well-known for the drug raid and the subsequent criminal prosecution than for his acting for a number of years.

He spoke to reporters about drug treatment during one court appearance and expressed his desire to quit drinking and doing drugs because he was “tired of paying the consequences” for his actions.

Regarding his recovery program, he said, “It’s definitely been an eye-opener.”

Renfro just finished filming a part in the Bret Easton Ellis book adaption “The Informers,” which also stars Winona Ryder, Brandon Routh, and Billy Bob Thornton.

“Brad was an exceptionally talented young actor and our time spent with him was thoroughly enjoyable,” said Marco Weber, president of the movie’s production company, Senator Entertainment, in a statement.