Los Angeles County Supervisor Sheila Kuehl told KPCC/LAist that Bryant's 13-year-old daughter, Gianna, was aboard the helicopter and also died. He said he thought it was a sheriff's helicopter on a training mission.
He and his teammate Shaquille O'Neal led the Lakers to three consecutive championships from 2000 to 2002.
The U.S. Federal Aviation Administration said the crashed helicopter was a Sikorsky S-76.
The retired Los Angeles Lakers star - who gave himself the nickname "Black Mamba" - opened the training facility in Thousand Oaks previous year.
The NBA lost one of the greatest to ever play the game today. "Much respect my brother", Bryant tweeted Saturday night.
In addition to their on-court competitions, they were also teammates on the Team USA squad that captured the gold medal at the 2008 Summer Olympics in Beijing. He was picked in the first round of the National Basketball Association draft by the Charlotte Hornets as the 13th pick following high school. "It can't be true", Kevin tweeted while Dwyane issued a similar sentiment by writing, "Nooooooooooo God please No!"
Before his passing, Bryant tweeted on Saturday, congratulating Lebron James on passing him as the third all-time scorer in the National Basketball Association. "Just an incredibly sad and tragic day". Five people are confirmed dead, TMZ reported.
President Donald Trump reacted to the reports soon after they began to surface, tweeting: "That is bad news!".