Pictured: Jet skier who was shot dead by his rescuer after falling into a South Carolina lake

Nathan Drew Morgan, 29, was shot dead last week when he became aggressive after elderly couple saved him

The day started out idyllically on Lake Keowee in western South Carolina, a gorgeous spot with stunning views of the Blue Ridge Mountains, its shores filled with sprawling mansions and its waters dotted with boaters, fishermen and locals enjoying the Spring Break sunshine.

One couple in their 20s headed out on jet skis. Another 50 years their senior took to the water on a pontoon boat.

Their paths would unexpectedly cross on 15 March out on Lake Keowee. And one man would end up dead.

Nathan Drew Morgan, 29, lived nearby in Walhalla, about a 15-minute drive west. He headed out on a jet ski with a female companion two days before St Patrick’s Day; his only son was about to turn 10.

Nathan Drew Morgan was mourned by friends online (nathan)

Meanwhile, a 74-year-old man and his wife also headed out on the lake, enjoying the mild weather on a pontoon boat.

What exactly happened on the water remains unclear; investigators suggest Morgan and his unnamed companion may have gotten into an altercation - but whatever occurred, they ended up on the water without lifeboats, the jet ski circling.

The pontoon couple saw them floundering and drove the boat over to help, according to the Oconee County Sheriff’s Office. They pulled Morgan and his companion from the water - but the dramatic scene was only about to worsen.

Morgan “became agitated and began assaulting the couple on the pontoon,” the sheriff’s office wrote in a release. “Investigators have been told that the man may have wanted to get back to the Jet Ski.”

His companion “attempted to de-escalate the assault” by pushing Morgan back into the water, but the couple helped him back onto the boat a second time. That’s when his aggression continued and the 74-year-old “shot the man fearing for his and his wife’s life while being assaulted.”

Morgan and a female companion were on a jet ski in Lake Keowee, a popular destination, while an elderly couple were on a pontoon boat (Getty Images/iStockphoto)

Morgan died on that pontoon boat from a gunshot wound to the chest - less than a week before the birthday of his son, Bentley.

Sheriff Mike Crenshaw told The Journal of Seneca that Morgan may have been intoxicated

Investigators declined to file charges against the 74-year-old, ruling that the shooting was self-defense. The names of the elderly couple have not been released as they continue to grapple with the tragic situation, as does the pleasant resort community.

The Oconee County Sheriff’s Office also asked for “continued prayer” for the family of Morgan, described in his obituary as a man who “enjoyed being on the water, fishing, sitting around a campfire, and playing basketball.”

A native of Asheville in neighbouring North Carolina, the 29-year-old was a member of Flat Shoals Baptist Church and is survived by his father and son, the obituary reads.

Local man Michael Davitt told NBC affiliate WYFF4 that he watched the scene unfold from his backyard and called 911.

“This is a pretty crazy incident, I’d say pretty much anywhere, especially for a Tuesday,” Mr Davitt said.

He described “fisticuffs” and “a lot of swearing” before a shot rang out and he called authorities.

“I was screaming with them like, ‘What’s going on? Do you guys need any help?’” he said. “While on the phone with 911.”

He continued: “It was kind of more of a shocking moment for me, witnessing this entire thing because I wasn’t really sure what it was.”

On Facebook, tributes poured in for the late 29-year-old.

One childhood friend, Dillon Queen, wrote that he and Morgan had been “best friends even brothers.”

“If you knew Drew you would know one thing, and that is he was hard headed,” Mr Queen wrote. “He would argue with you about anything and everything if he thought he was right about it and if something was done a certain way he would argue it was wrong and that it should be done this way.

“I wouldn’t trade him for anything different though.”

He continued: “Yesterday was such a shock. I’ve had so many mixed emotions about all this. I’ve been sad to mad to crying to laughing about old times. It is just so hard to realize he isn’t here anymore ... Idk what happened on that boat yesterday but what I do know is my hard headed fearless loving brother is gone.”