Photographs from FBI files of the Chevrolet Impala, which had been assigned to FBI agent Matthew Lowry, in which heroin and other evidence was found. Some areas were redacted by court officials to prevent disclosure of sensitive information. (U.S. District Court)

A former FBI agent in the Washington Field Office pleaded guilty Tuesday to stealing heroin that had been collected as evidence, and in his first public comments, he apologized and warned against the scourge of drug addiction.

“Today I informed the court of criminal acts of misconduct that I committed while trying to handle my pain medication,” Matthew Lowry told reporters outside the D.C. federal courthouse. “I want to apologize and say I was wrong.”

The 33-year-old agent said only a few words during the hour-long court proceeding in which he pleaded guilty to 64 criminal charges, including obstruction of justice, tampering with evidence and possession of heroin. He could be imprisoned for seven or more years when he is sentenced June 29, although his defense attorney will argue for less time.

After the hearing, the fired agent stood with his father, a retired assistant police chief, and spoke briefly and calmly about his personal and professional fall. His attorney has said Lowry became addicted to powerful pain medication wrongly prescribed to treat potentially debilitating ulcerative colitis and that he turned to heroin to self-medicate.

“Hopefully from this situation I’ll be able to stand as an example of how not to deal with prescription pain medication abuse and be able to help people understand how powerful and addictive and dangerous they can be,” Lowry said. Asked how he was holding up, he paused and said, “I’m getting better.”

A look at how Agent Lowry affected the case of Earl Owens, who was eventually dismissed.

Lowry was caught at the end of September when he didn’t return home after work. Fellow agents found him nearly incoherent standing outside his agency car, which had run out of gas in a vacant lot near the Navy Yard in Southeast Washington. Agents later found drugs in open evidence bags in the car.

The theft of heroin from three drug cases­ over the course a year forced federal prosecutors to dismiss cases against 28 defendants, many of whom had already been convicted and sentenced to prison. Cases against 150 more defendants were investigated but not dropped.

Lowry, in a statement issued by his attorney after charges were filed March 20, stated his regret about ruining investigations and said he had helped investigators by walking them through how he stole drugs undetected for about a year.

Hundreds of pages of documents obtained by The Washington Post show that Lowry took advantage of procedures that allowed a single agent to sign out drugs for lab analysis and did not involve tracking whether the packages reached their purported destination. Lowry was able to store drug evidence in his car, sometimes for as long as a year, with no questions asked. Lowry described how he forged signatures of agents on forms, repackaged drugs in bags and used laxatives to replace heroin he had taken to avoid discrepancies in weight.

Tuesday was Lowry’s first court appearance and the first time he has addressed the allegations in public. Most of the details of what Lowry did and how he did it have already been publicized, and his attorney, Robert C. Bonsib, had previously said the former agent would plead guilty.

The hearing before U.S. District Judge Thomas F. Hogan was straightforward and perfunctory. The judge read through brief details of each of the 64 charges and asked Lowry whether he had committed the offenses and understood the ramifications of pleading guilty.

“Once I accept this, it is very hard to retract,” Hogan warned Lowry. “There is no rethinking this matter.”

Photographs from FBI evidence files of heroin found in the car assigned to FBI agent Matthew Lowry. Prosecutors dropped drug cases against 28 defendants in four cases based on evidence now deemed tainted. (U.S. District Court)

Lowry answered him the way he had answered most all questions in court: “Yes, your honor.”

Hogan, with no objection from the prosecutor, allowed Lowry to remain free until his sentencing, although he will have to go through a formal booking with fingerprinting and a mug shot in the coming days. Hogan did order Lowry, who is undergoing extensive drug rehabilitation, to submit to drug tests.

Bonsib told the judge that the former agent just moved into a new house with his wife and infant child and that his father is with him every day. Only his father, William Lowry, came to court Tuesday; the rest of the family worried that the proceedings would be too emotional, Bonsib said, although they will be present for sentencing.

At the end, Lowry emerged from the courthouse as a light rain fell. His 64-year-old father stood by his side, silent but offering support.

Lowry told reporters that “opiate addiction has no boundaries.” He was speaking of prescription pain drugs in the same class as heroin. “I think it’s one of the greatest epidemics as far as drugs,” Lowry said. “Anybody can get addicted to this medication.”

The former agent answered a few other questions and then walked away, his attorney to his left and his father to his right, his father’s left arm around his son’s back.