Naomi Osaka was left "petrified" after reports of an active shooter being present at the fight between Gervonta Davis and Rolando Romero in New York.
Tennis star Osaka was at the Barclays Center in Brooklyn, where Davis retained his WBA lightweight title with a sixth-round stoppage of fellow American Romero.
However, reports of an active shooter inside the venue sparked panic. Though this speculation later proved unfounded, ESPN reported that a security supervisor for the venue had said there was a person with a gun in the concourse.
Osaka detailed her experiences of being in the arena at the time, revealing she had to take cover in a closed-off room.
"I was just in the Barclays Center and suddenly I heard shouting and saw people running, then we were being yelled at that there was an active shooter and we had to huddle in a room and close the doors, I was so f****** petrified man," the former world number one posted on Twitter.
Osaka followed her initial post up 11 minutes later confirming she had exited the Barclays Center.
"I really hope everyone made it out safely, since I'm tweeting this we made it out ok," she added.
The United States is still reeling from a school shooting in Uvalde, Texas earlier this week in which 19 children and two teachers were killed.
In the wake of the tragedy, multiple high-profile sportspeople, including Golden State Warriors coach Steve Kerr, have called for changes to gun laws in the US.