Thousands of people converged on a Dallas street Saturday where U.S. president John F. Kennedy was assassinated exactly 40 years ago.

Many left flowers, flags and messages of mourning near the site – one of several makeshift memorials across the country.

The mood was solemn as people wandered by an "X" on the pavement that marks the spot Kennedy's convertible limousine passed when he was hit around 12:30 p.m. on Nov. 22, 1963.

Pausing to remember at Kennedy's grave at Arlington National Cemetery
Pausing to remember at Kennedy's grave at Arlington National Cemetery

"John F. Kennedy has been gone nearly as long as he lived, yet the memory of him still brings pride to our nation and a feeling of loss that defies the passing of years," U.S. President George W. Bush said in a written statement.

Near Washington, thousands gathered at his grave in Arlington National Cemetery. The site was closed earlier in the morning so relatives – including daughter Caroline Kennedy – could hold a private service with the local Roman Catholic archbishop.

"Even though it was 40 years ago, it's still with us. It changed America. It changed the world," said one man.

"I remember thinking that it was not possible that a president could actually be shot," recalled another man. "It scared me as a child."

According to officials, Lee Harvey Oswald gunned down Kennedy. They said he fired the shots from the sixth floor of what was then the Texas School Book Depository.

But decades later, polls suggest that two-thirds of Americans remain unconvinced that Oswald acted alone. Conspiracy theories range from a mob-orchestrated hit to an assassination planned by Communists.