Craig Cassidy, The Union Democrat

Seven members of the Smith family set out last Tuesday morning for a challenging hike up Yosemite National Park's Mist Trail and, along the way, conversation invariably turned to the 2011 deaths of three tourists swept over Vernal Fall and similar accidents there.

It hadn't then occurred to the group, hailing from San Jose and Indiana, that, when they reached the top of the waterfall, they'd almost witness such a tragedy.

But about 12:30 p.m., after snapping a series of family photos next to the waterfall's overlook, and chatting about their adventure, a sense of dayhiker triumph turned to terror.

"My baby, my baby," a woman shrieked.

It was a strange and disorienting moment any of the Smiths is unlikely to forget.

A young boy had fallen into the Merced River, just upstream of the fall. His name was Alex and he was age 9, from what the Smiths were later able to ascertain. He had apparently dropped a water bottle into the river and was attempting to snatch it when he fell in.

As stunned witnesses watched on, the red-shirted boy bobbed through the rapids near the river's edge. At one point, he slowed when he hit a rock, but then continued to be whisked uncontrollably toward the 317-foot drop that has claimed more than a dozen lives in the past decade.

"It took a second to realize what was happening," explained Justin Smith, a Silicon Valley electronic engineer whose family has vacationed at Yosemite yearly for the past several years. His sister-in-law and brother-in-law joined them this year - their first time visiting the park.

"It took a second or two to realize it was a person. … He was bobbing up and down into whitewater," explained Justin Smith. "He had this sheer look of panic and fear."

Before Smith or the boy's father could react, Smith's son, Alec Smith, 16, was at the river's edge.

"My wife yelled, 'no Alec, get out of there.'"

The husky high school football player had jumped the guard rail and lowered himself partway into the water, clinging to a dry rock with one hand.

He was about 20 to 30 feet from the waterfall's edge, on a small outcrop, Justin Smith explained.

"He was reaching out with his left arm and told the boy, 'grab on to my hand.' I can imagine the boy was in sheer panic… but he got a hold of the boy."

The boy's father then grabbed Alec's shirt while Justin Smith headed a little farther downstream to catch anyone should they slip.

Smith reckons his son is a hero. He was back in school Monday, though, and unavailable for comment.

"It was close. It was waaay too close," said Justin Smith, pondering what could have been.

"That little boy would be gone if Alec hadn't reacted that fast. It all worked out with the best outcome. He was in the best place at the best time."

For about 45 minutes after the rescue, both families huddled in their respective camps, at least mildly shocked by what had unfolded in an extremely stressful flash.

The boy's family changed some of his clothes, then they went to the Smiths to thank them.

While they didn't exchange names, Justin Smith said, the Smiths got the boy's first name and learned he had an identical twin brother named Alan.

"Alex reached his hand out and said to Alec, 'thank you for saving my life."

The families snapped some photos and then parted ways. The Smiths decided to forgo another night roughing it at Curry Village, where they'd been since Sunday, and stayed instead at the Tenaya Lodge.

"It was good. … We probably weren't ready to drive home yet."

A few lessons can be gleaned from last Tuesday's events, according to park spokesman Scott Gediman, whose office learned of the incident when media inquires started pouring in Friday.

First thing to know: Be careful around water - especially the cold, fast moving currents coursing through the park's rivers and streams this time of year. Gediman said the park's rivers right now are nearing peak flows, because of the low snowpack and warm temperatures.

Too, people need to be very careful if attempting to assist a person who's in trouble.

The August 2011 waterfall accident happened when one man, posing for a photo, fell in the water, only to be joined by two friends who'd fallen in while attempting to grab and rescue him.

All three, members of a Central Valley church group, went over the edge as frustrated onlookers watched.

"We wouldn't discourage people," from helping others, Gediman said. "We're just thankful they are OK."