The fog was so dense in the Los Angeles area that it grounded police and sheriff’s aircraft. But the helicopter carrying basketball legend Kobe Bryant, his 13-year-old daughter Gianna, and seven others was given special clearance to fly on Sunday morning.

When the chopper crashed, visibility in the vicinity was reduced to two to three miles, according to National Weather Service data — a factor likely to figure into the National Transportation Safety Board’s investigation of the fatal crash.

The board also will look into any mechanical problems, and experts say if there were any, they would have been exacerbated by the conditions. It was not known when the NTSB would conclude its investigation, officials said Monday night.

“Any emergency is amplified when you can’t see your surroundings,” aviation consultant William Lawrence told the Los Angeles Times.

The helicopter crashed into a hillside shortly before 10 a.m. and burst into flames.

Shock waves continued to ripple through the sports world and the Philadelphia area. Former 76ers star Allen Iverson said he was “devastated” by the news.

“This is like losing a family member,” said NBA Hall of Famer and current TNT analyst Charles Barkley.

Before he became a Los Angeles Laker, Bryant was a sensation at Lower Merion High School. But what stayed with former teammate Guy Stewart was Bryant’s ingenuousness.

“He was so funny and down to earth,” Stewart said Monday as former Aces players gathered at Lower Merion High’s gym to reminisce. “That’s what I always told anybody who asked about him: ‘He was just a down-to-earth guy.’”

» READ MORE: Kobe Bryant's Lower Merion coaches and teammates knew it was all special

Bryant, 41, had retired from the NBA, but basketball never left his blood. It came back with a vengeance, he said, when Gianna, one of his four children, started playing.

The Bryants were headed to a basketball game where Kobe was expected to coach and Gianna to play. The other victims have been identified as John and Keri Altobelli and their daughter Alyssa, a teammate on Gianna’s Mamba Academy basketball team; Christina Mauser, Mamba’s top assistant coach; and Sarah Chester and her 13-year-old daughter, Payton, another Mamba player.

The pilot, Ara Zobayan, was qualified to fly in adverse weather as well as to instruct others how to navigate poor conditions.

Kobe Bryant had said he frequently commuted by helicopter to avoid the Los Angeles region’s notorious traffic jams so he could spend more time with his family. Zobayan was his regular pilot.

On Sunday morning, the weather service reported that a dense layer of marine air created a persistent visibility-reducing fog. But according to audio records between the pilot and the tower at Hollywood Burbank Airport captured by the website, the helicopter had Special Visual Flight Rules clearance to fly.

» READ MORE: When Kobe was 14, The Philadelphia Inquirer predicted: ‘Remember this name’

Experts said that the fact that the S-76B craft, favored among celebrities and business executives, was 29 years old would not have been a concern as long as the helicopter was properly maintained. It was owned by Island Express Holding Corp., which registered the helicopter in 2015, according to the helicopter database

The records show the aircraft was previously owned by the State of Illinois, and was likely used to transport the governor.

Flight-path data collected by flight-tracking service Flightradar24 shows the helicopter taking a circular route from John Wayne Airport in Orange County northwest toward Thousand Oaks. It cut across the broad coastal plain of central Los Angeles before going north. The preliminary data suggest the aircraft, which crashed about 40 minutes after takeoff, briefly climbed to an altitude above 2,500 feet before it descended at a high rate before the crash.

It likely will take several weeks for federal investigators to determine the cause of the crash.

And those who knew Bryant suggested it would take far longer to comprehend and get over what happened.

Among other traits, on Monday they recalled Bryant’s incredible work habits.

“Never have I witnessed such passion, work ethic, and intensity — such a unique and purposeful drive for greatness,” Lower Merion basketball coach Greg Downer said Monday night. “No excuses. No shortcuts. No days off.”

» READ MORE: Philly-area dads who coach their daughters: ‘Many of us can relate to Kobe the father’

“I remember, I was a freshman and I showed up at the gym one day, sort of out of the blue, and Kobe Bryant was there practicing,” said Steve Meehan, a Lower Merion basketball player in the Class of 2008. “I had heard the stories of Kobe getting here at 5:30 in the morning before school, and to show up as a freshman and see this person who had an NBA game later that day in our gym was an amazing inspiration.”

Iverson told of when he and Bryant were rookies in 1996 and the 76ers were playing the Lakers in Los Angeles.

“He came to my hotel, picked me up, took me to a restaurant,” Iverson said. “When we returned before he left, he asked me, ‘What are you going to do tonight?” My reply was‚ ’I’m going to the club. What are you going to do?' He said, ‘I’m going to the gym.’"

Sandy Betegh, who taught Spanish at Lower Merion High and had Bryant as a student, said at her home in Broomall on Monday that she was “still coming to terms with the fact he left.”

“There are some kids in your life that get into your heart. And they will always be there,” she said, tears coming to her eyes.

Staff writers Phil Anastasia, Maddie Hanna, Anna Orso, Ellie Rushing, Keith Pompey, and Anthony R. Wood contributed to this article, which also contains information from Inquirer wire services.