Ronald Kessler, a former Washington Post and Wall Street Journal investigative reporter, is the New York Times bestselling author of The First Family Detail: Secret Service Agents Reveal the Hidden Lives of the Presidents and The Secrets of the FBI.

FBI agents investigating the death of Bill Clinton's Deputy White House Counsel found that Hillary Clinton 'triggered' his suicide when she attacked and humiliated her mentor from their former Rose Law Firm in front of other White House aides a week before he took his own life.

Vince Foster's suicide has been the focus of much speculation since he shot himself in a Virginia park in 1993, as Donald Trump pointed out in a recent interview.

'It's the one thing with her, whether it's Whitewater or whether it's Vince or whether it's Benghazi. It's always a mess with Hillary,' Trump said.

But former FBI agents believe they had the story straight.

Foster committed suicide on July 20, 1993 in Ft. Marcy Park along the Potomac River by placing a .38 caliber revolver in his mouth and pulling the trigger.

The FBI investigation into his death was conducted as part of independent counsel Kenneth W. Starr's probe of the Clintons' investments in the Whitewater real estate development.

The FBI found that a week before Vince Foster's suicide, First Lady Hillary held a meeting at the White House with Foster and other top aides to discuss her proposed health care legislation during which she berated the lawyer

Hillary violently disagreed with a legal objection Foster raised at a meeting on her health care proposal and ridiculed him in front of his peers, says former FBI agent Coy Copeland

The Whitewater scandal came about in the late 1970's when the Clintons partnered with friends James and Susan McDougal to purchase 220 acres of land in Arkansas that would become the Whitewater Development Corporation.

The venture failed, thousands of dollars were lost, and James McDougal moved on to start Madison Guaranty Savings and Loan.When federal regulators began to investigate another McDougal deal, questions about the Clintons' involvement in the Whitewater arose during President Clinton's first term in office. An investigation into the legality of the Whitewater transactions was launched.

The investigation, led by special prosecutor Robert B. Fiske, and then Kenneth Starr.

But for unknown reasons, Starr elected to conceal the FBI's findings about Vince Foster in his final report.

In interviews for my book The First Family Detail, the FBI agents revealed the truth about Foster's death on July 20, 1993 when he shot himself at Fort Marcy Park along the Potomac River.

Foster committed suicide on July 20, 1993 in Ft. Marcy Park along the Potomac River by placing a .38 caliber revolver in his mouth and pulling the trigger

In interviewing Clinton White House aides and Foster's friends and family, the FBI found that a week before Foster's death, Hillary held a meeting at the White House with Foster and other top aides to discuss her proposed health care legislation.

Hillary violently disagreed with a legal objection Foster raised at the meeting and ridiculed him in front of his peers, former FBI agent Coy Copeland and former FBI supervisory agent Jim Clemente told me.

Copeland was Starr's senior investigator and read the reports of other agents working for Starr.

During the White House meeting, Hillary continued to humiliate Foster mercilessly, both former FBI agents say.

'Hillary put him down really, really bad in a pretty good-size meeting,' Copeland says. 'She told him he didn't get the picture, and he would always be a little hick town lawyer who was obviously not ready for the big time.'

Indeed, Hillary went so far as to blame Foster for all the Clintons' problems and accuse him of failing them, according to Clemente, who was also assigned by the FBI to the Starr investigation and who probed the circumstances surrounding Foster's suicide.

'Foster was profoundly depressed, but Hillary lambasting him was the final straw because she publicly embarrassed him in front of others,' says Clemente, speaking about the investigation for the first time.

'Hillary blamed him for failed nominations, claimed he had not vetted them properly, and said in front of his White House colleagues, "You're not protecting us" and "You have failed us," Clemente says. 'That was the final blow.'

Vince Foster shot himself at Fort Macy Park a week after the meeting with Clinton

The second civil war canon that overlooked the embankment where Vince Foster's body rested after his suicide at Fort Marcy Park

After the meeting, Foster's behavior changed dramatically, the FBI agents found. Those who knew him said his voice sounded strained, he became withdrawn and preoccupied, and his sense of humor vanished. At times, Foster teared up.

He talked of feeling trapped. On Tuesday, July 13, 1993, while having dinner with his wife Lisa, Foster broke down and began to cry. He said he was considering resigning. That weekend, Foster and his wife drove to the Eastern Shore of Maryland, where they saw their friends, Michael Cardoza and Webster Hubbell, and their wives.

'They played tennis, they swam, and they said he sat in a lawn chair, just kind of sat there in the lawn chair,' Copeland says. 'They said that just was not Vince. He loved to play tennis, and he was always sociable, but he just sat over in the corner by himself and stared off into space, reading a book.

Two days later, Foster left the White House parking lot at 1.10 p.m. The precise time when he shot himself could not be pinpointed. After Park Police found his body, they notified the U.S. Secret Service at 8.30 p.m.

Based on what 'dozens' of others who had contact with Foster after that meeting told the agents, while Foster was already depressed, 'the put-down that she gave him in that big meeting just pushed him over the edge,' Copeland says. 'It was the final straw that broke the camel's back.'

No one can explain a suicide in rational terms. But the FBI investigation concluded that it was Hillary's vilification of Foster in front of other White House aides, coming on top of his depression, that triggered his suicide about a week later, Copeland and Clemente both say.

Starr issued a 38,000-word report, along with a separate psychologist's report on the factors that contributed to Foster's suicide.

Yet Starr never mentioned the meeting with Hillary, leaving out the fact that his own investigation had found that Hillary's rage had led to her friend's suicide.

President Clinton, Hillary and daughter Chelsea, leave St. Andrew's Catholic Cathedral with Father George Tribou in Little Rock, Arkansas, July 23, 1993, after funeral services for Foster

The FBI investigation concluded that it was Hillary's vilification of Foster in front of other White House aides, coming on top of his depression, that triggered his suicide about a week later, Copeland and Clemente both say.

Why Starr chose to not reveal the critical meeting and his own investigators' findings remains a mystery.

While the Clintons claimed Starr was out to get them, Clemente says that as his staff hanged, Starr vacillated between pursuing the investigation aggressively and pulling his punches.

For example, the former FBI supervisor agent reveals that Starr refused to allow him to try to interview Hillary about her commodities trading.

For reasons still unknown, in her first commodity trade in 1978, Hillary was allowed to order ten cattle futures contracts, which would normally cost $12,000, although she had only $1,000 in her account at the time, according to trade records the White House released.

Hillary was able to turn her initial investment into $6,300 overnight. In ten months of trading, she made nearly $100,000. She claimed she made smart trades based on information from the Wall Street Journal.

The question, Clemente says, was why she was allowed to make investments while ignoring normal margin calls that require traders to cover any losses incurred during the course of trading.

Starr issued a 38,000-word report, along with a separate psychologist's report on the factors that contributed to Foster's suicide. Yet Starr never mentioned the meeting with Hillary, leaving out the fact that his own investigation had found that Hillary's rage had led to her friend's suicide

Starr's report recounted how the FBI ran down even the most bizarre theories about Foster's death and conducted extensive ballistics tests that refuted assertions that Foster had not committed suicide.

Starr retained Dr. Brian D. Blackbourne, a forensic pathologist who is the medical examiner for San Diego County, California, to review the case.

He concluded that 'Vincent Foster committed suicide on July 20, 1993 in Ft. Marcy Park by placing a .38 caliber revolver in his mouth and pulling the trigger. His death was at his own hand.'

Starr also retained Dr. Henry C. Lee, an expert in physical evidence and crime scene reconstruction who then was director of the Connecticut State Police Forensic Science Laboratory.

He reported that after a 'careful review of the crime scene photographs, reports, and reexamination of the physical evidence, the data indicate that the death of Mr. Vincent W. Foster Jr. is consistent with a suicide. The location where Mr. Foster's body was found is consistent with the primary scene,' meaning the place where he committed suicide.

But in his report, Starr never referred to the meeting where Hillary humiliated Foster in front of aides, nor to the change in his disposition after that.

Former FBI supervisory agent Jim Clemente (above) told Ron Kessler Hillary violently disagreed with a legal objection Foster raised at the meeting and ridiculed him in front of his peers

Starr never told Copeland or Clemente why he decided to exclude the material from his report, and the former FBI agents can only speculate on his reasoning.

'Starr was a very honorable-type guy, and if it did not pertain to our authorized investigation, he did not want to pursue it,' Copeland says. 'And I think he felt that Hillary's personality and her dealings with subordinates in the White House were immaterial to our investigation.'

'Starr didn't want to offend the conscience of the public by going after the first lady,' Clemente says. 'He said the first lady is an institution. He acted most of the time as a judge instead of as an investigating prosecutor, and then he hired attorneys who went to the other extreme.'

Asked why he excluded the reasons for Foster's suicide from his report, Starr did not respond. A spokesman for Hillary Clinton had no comment.

While Starr refused to allow FBI agents to try to interview Hillary, Copeland recounts one encounter with her. It underscores why, as detailed in The First Family Detail, Secret Service agents consider being assigned to Hillary's detail a form of punishment because she is so nasty.

As he was serving a subpoena in the Eisenhower Executive Office Building adjacent to the White House, Copeland says, another FBI agent working on the Foster investigation made the mistake of saying hello to Hillary as she passed him.

'She had a standing rule that no one spoke to her when she was going from one location to another,' Copeland says. 'In fact, anyone who would see her coming would just step into the first available office.'

But the agent 'didn't know the ground rules,' Copeland says. 'He dared to speak to her in the hallway,' he says. 'As he was leaving, she got out of the elevator and was approaching him.'

'Good morning, Mrs. Clinton,' the agent said.

'She jumped all over him,' Copeland says. "How dare you? You people are just destroying my husband."

'It was that vast right-wing conspiracy rant. Then she had to tack on something to the effect of, "And where do you buy your suits? Penney's?'

For many weeks, the agent told no one about the encounter.

'Finally, he told me about it,' Copeland says. 'And he said, "I was wearing the best suit I owned."'