William C. Sullivan, once the third-ranking official of the FBI and then an outspoken critic of the late J. Edgar Hoover and his policies, was killed in a hunting accident yesterday near his home in Sugar Hill, N.H. He was 65.

Police said Mr. Sullivan was shot while deer hunting in the White Mountains. They identified the other hunter as Robert Daniels, about 20, of Lisbon, N.H. The incident was still under investigation last night and no charges had been filed against Daniels.

William Clarence Sullivan, a farm boy from Bolton, Mass., entered the FBI as a special agent on Aug. 4, 1941. By the time the late J. Edgar Hoover had forced him to retire on Oct. 6, 1971, Mr. Sullivan was the assistant to the director for all the bureau's investigative activities.

His 30 years of service saw enormous changes in the FBI, its place in American government, and how it was regarded by some other parts of the government - notably Congress - and by some portions of the American public.

When Mr. Sullivan joined the bureau, the FBI saw itself - and was seen by others - as a crime-fighting organization and as the country's first line of defense against Nazis and other subversives. By the time he left, the bureau was coming under uncreasing attack for violating the rights of American citizens. Many of these charges have since been substantiated and the myth of Hoover himself has been dispelled.

Mr. Sullivan played a role in these transformations, first as a loyal lieutenant of Hoover who intiated many of the abuses that have been uncovered ny Congress and the press in recent years, and then as a bitter critic of his late boss.

In an interview with The Los Angeles Times in 1973, Mr. Sullivan called Hoover "a master blackmailer." He suggested that the director had lost control of himself and was verging on senility before his death. A year later, Mr. Sullivan submitted a paper to a meeting of the Roscoe Pound-American Trial Lawyers Foundation in which he said that the FBI, as then organized, posed a threat to the civil liberties of the country.

"The weaknesses of the FBI have always been the leadership in Washington, of which I was a part for 15 years," he wrote. "I accept my share of the blame for its serious short-comings."

For 10 of the 15 years during which Mr. Sullivan described himself as a member of the top leadership of the FBI, he was an assistant director in charge of domestic intelligence operations.

In this capacity, he played a role in numerous abuses by the FBI that have been documented by the Senate Intelligence Committee headed by Sen. Frank Church (D-Idaho). These include "black bag" operations, or burglaries carried out by FBI agents; "Cointelpro," the counter intelligence program against such groups as the Ku Klux Klan, the Black Panthers and other black groups, antiwar groups during the Vietnam era, and the "New Left"; the tapping of the telephones of 17 members or former members of the National Security Council staff and of reporters, which were illegal taps designed by the Nixon White House to plug news leaks, and a broad range of other activities aimed at "dissident" groups within the United States.

The final report of the Church Committee quotes the following passage from Mr. Sullivan's testimony:

"Never once did I hear anybody, including myself, raise the question, 'Is this course of action which we have agreed upon lawful, is it legal, is it ethical or moral?' We never gave any thought to this line of reasoning, because we were just naturally pragmatic."

For his part in this "pragmatism," Mr. Sullivan was investigated extensively by the Watergate special prosecutor's office. The question was this: had Mr. Sullivan conspired to remove from FBI files and sol-called "Kissinger" wiretaps on the 17 National Security Council aides and reporters for the purpose of concealing these taps from U.S. District Judge W. Matt Byrne?

Judge Byrne was presiding over the trial of Daniel Ellsburg, who released the famous "Pentagon papers" to the press in 1970. When it was learned that Ellsburg had been overheard on one of these taps, Judge Byrne dismissed the charges against him.

In fact, Mr. Sullivan had removed these files from the FBI just before he went into retirement, and turned them over to Robert C. Mardian, a former assistant attorney general in charge of internal security. The files ended up in the Nixon White House.

Mr. Sullivan said that he had taken the files because he feared that Hoover would try to use them to "blackmail" President Nixon into keeping Hoover in his job indefinitely.

On Sept. 16, 1975, the Watergate special prosecutor's office wrote to Mr. Sullivan's attorney that "the special prosecutor has examined the evidence (of alleged conspiracy) against Mr. Sullivan and has concluded that the evidence does not warrant the bringing of any criminal charges against Mr. Sullivan."

Since his forced retirement in 1971, Mr. Sullivan repeatedly has stated the view that the top FBI officials - not the field agents - should be held responsible for violations of the law committed in the name of the bureau.

Last summer, he testified before a federal grand jury in New York that has brought charges against John J. Kearney, a retired supervisor of the FBI's New York field office. Kearney was indicted last April on charges that he helped direct mail-opening and wiretapping operations. The case has not yet gone to trial.

Mr. Sullivan acquired a reputation through his career in the FBI as an intellectual and an expert on communism. His views on the Communist Party of the U.S.A. led to his break with Hoover. In 1970, Mr. Sullivan told a meeting of United Press International editors that "radical organizations," such as the Weathermen faction of the Students for a Democratic Society, presented a greater threat to the country than the Communists.

Hoover reportedly remonstrated with Mr. Sullivan on the ground that the FBI's budget was based on the alleged threat of communism and that Mr. Sullivan's remarks undercut this position. Mr. Sullivan declined to retract his statements and told him that Hoover himself knew them to be true.

After leaving the FBI, Mr. Sullivan worked briefly in private industry and then returned to the Justice Department to work on a drug enforcement project. In recent years he had lived in retirement in New Hampshire, although he was still a party to various civil suits growing out of FBI abuses at the time of his death.

[TEXT OMITTED FROM SOURCE] survivors include his wife, Marion, and two sons, Andrew and William, all of the home in Sugar Hill, and a daughter, Mrs. Mark D. Tuttle, of Simsbury, Conn.