WASHINGTON (AP) — Danny Defenbaugh's life was flying high on June 2, 1997.

On that day, the lead investigator of the Oklahoma City bombing, a man known in the FBI as "bureau to the bones," got engaged, celebrated the 28th anniversary of his first job with the agency and savored Timothy McVeigh's conviction in the crime.

Now Defenbaugh is surrounded by controversy, his work on the largest investigation in the FBI's history brought into question by the discovery that the bureau failed to give at least 3,235 pages of documents to McVeigh's attorneys.

Friends say Defenbaugh, 49, who received the Justice Department's top award for his work on the investigation, is taking it hard.

"I'm sure it is ripping his heart out," said Larry Mackey, a prosecutor in the McVeigh trial who is now in private practice.

"Even if the doors don't swing open and no conviction is changed — for Danny Defenbaugh, horrible damage has been done to his sense of self."

The document foul-up has halted McVeigh's execution until at least June 11 and could give rise to further delays.

The case was the biggest challenge of Defenbaugh's FBI career, which began June 2, 1969, when J. Edgar Hoover still directed the agency.

Paul Coggins, formerly the U.S. attorney in Dallas where Defenbaugh became special agent in charge in January 1998, describes him as a straight talker whose speeches tend to read like a police log.

"He's not exactly gruff, but he's not going to pussyfoot around a whole lot," Coggins said. "He gets to the point and gets to the point quickly."

He said Defenbaugh took pride in leading the investigation. "My guess is that it makes him sick to his stomach that these problems have arisen at this stage."

Defenbaugh, who grew up near West Rushville, Ohio, applied to the FBI while still a sophomore in high school. After graduation, he worked as a clerk at FBI headquarters in Washington. He later got a bachelor's degree in justice administration and a master's in forensic science.

Since becoming an agent in early 1976, Defenbaugh has helped solve kidnappings, extortion, hijackings and bombings.

As an FBI-certified bomb technician, he has traveled to more than 20 countries to help thwart international terrorism. Besides Oklahoma City, Defenbaugh has supervised more than 150 bombing investigations, including three terrorist attacks against U.S. installations in Beirut.

In the McVeigh case, according to a Senate staff memo from a briefing he gave to senators, he knew of a possible problem with missed documents for months before he told superiors. He said he wanted to see how bad the problem was first.

Dallas FBI spokeswoman Lori Bailey said Friday that for much of that time Defenbaugh knew only of a possible "administrative problem with the databases."

"He was not aware that there were materials there that were part of the discovery process," she said.

When FBI field offices were directed in December to forward their bombing files to Oklahoma City, a document surfaced that was not in the database maintained in Oklahoma.

Subsequent directives revealed more documents that weren't in the database.

In early May, about a week before McVeigh's scheduled execution, Defenbaugh told FBI officials in Washington that some materials hadn't been turned over to McVeigh's attorneys.

That led to a postponement of the first federal execution since 1963. The FBI says nothing in the sidetracked evidence casts doubt on McVeigh's guilt.

Mackey calls Defenbaugh a "delicate blend between a micromanager and long-range visionary" — a man who is attuned to detail, but doesn't let it distract him from the goal of an investigation: In this case, tracking down the bomber who killed 168 people in April 1995.

Defenbaugh declined an interview request on orders from FBI headquarters in Washington, but he told The Dallas Morning News earlier that the FBI needed to change how it deals with information.

"Investigatively, we didn't do anything wrong," he said. "Administrative errors — it's obvious that's something we made. And I thank God we caught them now because this storm will pass."

Oliver "Buck" Revell, former special agent in charge in Dallas, said Defenbaugh told colleagues he felt let down by other FBI personnel around the nation.