It all started when a 7-year-old girl slipped into the Niagara River off Squaw Island on Monday afternoon.

Her 17-year-old brother, identified today as Mustafa Ismail, jumped in after her and threw her to shore, into the waiting arms of two older sisters, witnesses said.

One of the sisters onshore – a 13-year-old – noticed her brother struggling in the water and jumped in after him.

Like her brother, she soon was overcome by the cold water and current.

At that moment, fisherman Leonard W. Stevens knew he needed to act as he saw the two siblings floating facedown about 20 feet from shore.

“I realized I had to save a life,” Stevens said.

Stevens managed to pull the 13-year-old sister from the water as he clung to a piece of driftwood, fearing that the river’s current might take his life. He tried for the brother, too, but the teenager, Stevens said, had disappeared into the brown water.

About 45 minutes later, a Buffalo police diver found the young man on the river’s bottom not far from where he had submerged.

A short time after that, the teen was pronounced dead at Erie County Medical Center.

Stevens was described by police as a hero, but the dramatic rescue was tempered by the death of the 17-year-old, who gave his life while saving his little sister.

Weeping, Stevens said, “He’s a hero in my book.”

“I consider Stevens and the brother both heroes for their actions. It’s unfortunate the brother lost his life, but he saved his sister,” Police Commissioner Daniel Derenda said late Monday.

Police said the the famils members are African immigrants, possibly from Somalia.

Stevens was at the river fishing Monday afternoon. He recalled seeing the sisters and brother kicking a ball around.

“There were three sisters and two brothers. Then I happened to see the little 7-year-old slip into the water and her older brother go in after her,” Stevens said, recounting the tragedy he had watched unfold.

Mustafa Ismail jumped into the river and was standing in water 3 feet deep when he snatched up his little sister.

“He grabbed the little girl and threw her to two other sisters on the shore,” said Stevens, a resident of nearby Hertel Avenue in the city’s Black Rock section, who had driven his bicycle to the park for an afternoon of fishing.

Stevens, 45, said the siblings still on the shore were screaming, “Save my brother! Save my brother!”

With his clothes on, Stevens leaped into the river and, hanging onto a log, made his way to the brother and sister still in the water, several hundred feet south of the International Railway Bridge. “I was holding onto a piece of driftwood, and I was able to get the sister and grab her and get her to shore,” said Stevens, who served eight years in the Navy.

Burmese native Halima Be said her husband, Solamal, waded into the water’s edge and grabbed the 13-year-old from Stevens. The sister was placed on her side on nearby grass, and Stevens performed first aid.

“She was gurgling, and I smacked her twice on the back, and she coughed up water and started breathing,” Stevens said.

According to police, the 7-year-old sister was standing “and screaming because she was cold and wet.”

Northwest District police arrived after Be called 911 at 3:01 p.m. with her cellphone, witnesses said.

Moments passed painfully slowly as two divers for the Buffalo police Underwater Recovery Team methodically searched the river’s bottom, just south of a concrete lookout protruding into the river.

Then, at about 3:55 p.m., approximately 45 minutes after the teenager had disappeared below the water, authorities said, a diver emerged.

The 17-year-old was found wedged between a rock and sticks on the riverbed, in a section where the bottom sloped from 8 feet deep to 20 feet, Stevens said police told him.

Stevens helped police and other first responders pulled the unconscious victim up the rocky shoreline.

Frantic efforts to revive the young man began immediately, with only a brief pause to shift the teenager onto a stretcher from a Rural/Metro Medical Services ambulance.

For a moment, when the young man was hauled out of the water, there was a sense of hope.

Stevens, who had been waiting anxiously on the shore, threw his hands up in jubilation as efforts to revive the teen were made.

“I began praying, ‘Lord, you gave him breath at birth, give him breath now.’ His siblings started praying with me,” Stevens said.

“I was hoping they could save him,” added Stevens, the father of three children ranging in age from 16 to 26. “When I went into the water, I was thinking of my own children and how I would want someone to rescue them.”

But it soon became clear that the young man would not regain consciousness, as somber-faced police officers and other rescue personnel walked silently past spectators, moments after the teenager was taken away. He was pronounced dead shortly after arriving at ECMC.

Bruno Lombardo, 20, and Don Plant, 22, said that watching the rescue efforts was heartbreaking.

“It’s crazy,” Plant said.

“I have no words to describe this,” Lombardo added.

One police officer at the scene said the dangers of the river cannot be emphasized enough.

“People don’t understand. You go in that water, you don’t come out,” the officer said. “The current is terrible.”