INDIANAPOLIS — Rich MacDonald was just a kid, trying to find his dad’s race number on the big screen through the flames and black mushroom clouds choking the track.

Only 6 years old, MacDonald, his grandfather and uncle had gone to the LA Sports Arena to watch the 1964 Indianapolis 500 live on closed-circuit television. Just two laps into the race, there was a fiery wreck and it was clear something had gone horribly wrong at Indianapolis Motor Speedway.

Rich MacDonald still remembers trying to find out if his father, American road racing champion Dave MacDonald, was in the wreckage.

“I really didn’t get it. There was lots of fire, lots of smoke,” MacDonald said. “I remember seeing little clues. I knew my father’s number was 83. And 83 was up there. My grandfather grabbed my uncle and me out of the stadium and into the lobby area. I knew at that point there was a problem.”

MacDonald would die later that afternoon and driver Eddie Sachs also was killed, a grisly reminder that the race has always been a life-and-death business.

Yes, the Indy 500 is “The Greatest Spectacle In Racing,” and Mario and Dario and milk and balloons have built an event steeped in festive tradition as it prepares to celebrate its centennial this weekend. But the race is also marked by tragedy. Just 12 laps into the inaugural race in 1911, mechanic Sam Dickson became the first to die and he certainly wasn’t the last.

Drivers, mechanics, fans, even a little boy standing across the street from the track long ago — all are part of the 500’s saddest chapter, painful memories of just how dangerous racing on the bricks and asphalt has been over the years.

At least 66 people have died because of auto racing since 1909 at the site, including 40 drivers, 14 mechanics and nine spectators. The 1930s was by far the deadliest decade with 21 deaths, while the ‘50s and ‘60s each saw eight people perish.

Back in ‘64, Dave MacDonald had lost control of his car and slammed into the inside wall. His car exploded into a fireball and slid back onto the track. Sachs hit MacDonald’s car head-on, and he was killed instantly, the track engulfed in so much fire and black clouds that it looked at IMS like a small town had burned down.

Nearly 2,000 miles away, Rich MacDonald tried to flip on a TV and watch the rest of the Indy 500 that would be won by A.J. Foyt. More than 50 friends and relatives had gathered at the family home in El Monte, California, many trying to give comfort to Rich and a younger sister.

MacDonald’s mother, Sherry, was at the track that day. Afterward, she withdrew from the racing community and could not imagine the idea of visiting the track again — until this year.

Rich MacDonald and Sherry; Sachs’ son, Eddie III, and Angela Savage, daughter of Swede Savage, the last driver to die in the race (1973), will all travel to the speedway this week and hope to pose for a group photo on the track. Angela Savage was born three months after her father died.

MacDonald said the group hopes to walk on the famed track and find a spot to honor their fathers — and do it with a smile. “We all had a loved one that was killed here, but it’s not going to define our lives,” Rich MacDonald said.