Shortly after leaving a party on Chappaquiddick Island, Senator Edward “Ted” Kennedy of Massachusetts drives an Oldsmobile off a wooden bridge into a tide-swept pond. Kennedy escaped the submerged car, but his passenger, 28-year-old Mary Jo Kopechne, did not. The senator did not report the fatal car accident for 10 hours.

On the evening of July 18, 1969, while most Americans were home watching television reports on the progress of the Apollo 11 lunar landing mission, Kennedy and his cousin Joe Gargan were hosting a cookout and party at a rented cottage on Chappaquiddick Island, an affluent island near Martha’s Vineyard, Massachusetts. The party was planned as a reunion for Kopechne and five other women, all veterans of the late Senator Robert F. Kennedy’s 1968 presidential campaign. Bobby Kennedy was Ted Kennedy’s older brother, and following Bobby’s assassination in June 1968 Ted took up his family’s political torch. In 1969, Ted Kennedy was elected majority whip in the U.S. Senate, and he seemed an early front-runner for the 1972 Democratic presidential nomination.

Just after 11 p.m., Kennedy left the party with Kopechne, by his account to drive to the ferry slip where they would catch a boat back to their respective lodgings in Edgartown on Martha’s Vineyard. While driving down the main roadway, Kennedy took a sharp turn onto the unpaved Dike Road, drove for a short distance, and then missed the ramp to a narrow wooden bridge and drove into Poucha Pond. Kennedy, a married man, claimed the Dike Road excursion was a wrong turn. However, both he and Kopechne had previously driven down the same road, which led to a secluded ocean beach just beyond the bridge. In addition, Kopechne had left both her purse and room key at the party.

Kennedy escaped the car and then dove down in an attempt to retrieve Kopechne from the sunken Oldsmobile. Failing, he stumbled back to the cottage, where he enlisted Gargan and another friend in a second attempt to save Kopechne. The three men were unsuccessful; her body was not recovered. The trio then went to the ferry slip, where Kennedy dove into the water and swam back to Edgartown, about a mile away. He returned to his room at the Shiretown Inn, changed his clothes, and at 2:25 a.m. stepped out of his room when he spotted the innkeeper, Russell Peachey. He told Peachey that he been awakened by noise next door and asked what time it was. He then returned to his room.

Was Kennedy trying to establish an alibi? In Leo Damore’s Senatorial Privilege–the Chappaquiddick Cover-up (1988), the author recounts an interview with Joe Gargan in which Gargan claimed that Kennedy had plotted to make Kopechne the driver and sole occupant of the automobile. Whatever Kennedy’s intentions, on the morning of July 19 he went back to Chappaquiddick Island and then returned to Edgartown. At 9:45 a.m., 10 hours after driving off Dike Road bridge, Kennedy reported the accident to Edgartown Police Chief Dominick Arena and admitted that he was the driver.

On July 25, Kennedy pleaded guilty to leaving the scene of an accident, received a two-month suspended sentence, and had his license suspended for a year. That evening, in a televised statement, he called the delayed reporting of the accident “indefensible” but vehemently denied that he been involved in any improprieties with Kopechne. He also asked his constituents to help him decide whether to continue his political career. Receiving a positive response, he resumed his senatorial duties at the end of a month.

There is speculation that he used his considerable influence to avoid more serious charges that could have resulted from the episode. Although the incident on Chappaquiddick Island helped to derail his presidential hopes, Kennedy continued to serve as a U.S. senator of Massachusetts into the 21st century. He died in 2009.

READ MORE: The Chappaquiddick Incident: What Really Happened?