The Berkeley Township Police Department identified the lifeguard as 19-year-old Keith Pinto of Toms River.
The tragic incident happened around 4:35 p.m. Monday in the area of 21st Avenue beach in South Seaside Park.
The Berkeley Township Police Department said four lifeguards, including Pinto, and four other beachgoers were "either struck or were injured by the residual lightning strike."
Police said Pinto succumbed to his injuries.
Ocean County Sheriff Michael Mastronardy said the injuries to the seven victims were not considered life-threatening.
"This young person was out there every day protecting the lives of others. Our lifeguard teams, like so many along the shore, develop special connections with our community throughout the summer, which makes this loss even greater," said Berkeley Township Mayor Carmen Amato.
Pinto's siblings tearfully remembered their brother in Toms River Tuesday morning.
"He was a perfect kid. He was amazing. He wanted to go to the Marines. He was going to Ocean County College because he wanted a degree first before he went," said the victim's sister, Tina Pinto.
Keith's twin brother Kevin is also a lifeguard. In years past, the two would be on the stand together.
"I was with him 24/7, so it's kind of crazy, it doesn't feel real right now," said Kevin.
The twins always worked together. This is the first year that they had different days off.
"We would drive together, drive home together, go out to lunch together, pretty much everything together. So now it's just crazy to see he's not here anymore," added Kevin.
An oceanside vigil was held Tuesday night for the 19-year-old lifeguard. The sound of mourning overshadowed the lull of the surf.
The dark beach was lit by hundreds of candles as mourners came out to South Seaside Park.
SEE ALSO: 'Bolt from the blue': How lightning can strike suddenly, even while sunny
The township's beaches are closed for swimming from Tuesday through Thursday as staff and lifeguards mourn the loss of their friend.
"Our hearts are with the family and friends of the young lifeguard killed by today's horrific lightning strike on the beach in Berkeley Township, and we pray for a full recovery for those injured," said New Jersey Governor Phil Murphy Monday night.
SEE ALSO: 16-year-old lifeguard dies after injury in Cape May, NJ
The identities of those injured by the lightning strike have not been released.
A handwritten note in purple ink was left with flowers Monday night at the base of a lifeguard stand at the beach.
"We were at the beach today and are grateful for what you've done for us by keeping us safe at the beach," the note read. "We are so sorry for your loss."
Pete Tortorelli was tending an outdoor bar a block away from the beach when, he said, lightning struck seemingly out of nowhere.
"It looked a little cloudy in one direction but clear as anything in the other direction, and it was the first lightning of the day," he said. "Literally two minutes after I saw the lightning, every cop car in this town was screaming down the street."
Thomas Taberoni was at a beachfront house 100 yards away from the lifeguard stand, noticing that it was beginning to get cloudy, when he heard what he described as the loudest noise he had ever heard.
"Have you ever been to an air show when they break the sound barrier with that boom and you weren't prepared for it?" he asked. "This was like 100 times louder than that."
Action News Meteorologist David Murphy says lightning can travel far and sideways.
"Lightning can travel laterally away from a thunderstorm and it can actually go 12,13,14 miles or more. Maybe even 20, 25, and that's farther than the sound of thunder travels," said Murphy.
According to the National Lightning Safety Council, Monday's tragedy was the ninth known lightning fatality of the year in the U.S. and the second in New Jersey. Michael Ward, 70, of Florence was struck and killed by lightning while on a golf course at the Burlington Country Club in Westampton Township in June.
This is the second young New Jersey lifeguard who has died in recent weeks. On August 19, Norman Inferrera, a rookie lifeguard in Cape May, was rowing a lifeguard boat when a wave knocked him unconscious. He died at the hospital days after the accident.
Cape May officials are now re-examining the use of surfboats following Inferrera's death. The Press of Atlantic City reports that Cape May lifeguards won't train or use the boats for the rest of the year amid a re-examination of their role.
The Associated Press contributed to this report.