Former British women's tennis number one Laura Robson was among those at a Las Vegas concert where a gunman opened fire and left at least 58 people dead and more than 500 injured.
The Australian-born British left-hander, ranked 249th in the world and coming off a loss at an event in California on Friday, tweeted that she and a friend were in the crowd when gunfire began.
"I'm okay," she tweeted. "We were right there.. sounded like fireworks at first then everyone started running. Scary shit.
"My friend who was deeper in crowd has been helping people who were shot. We're all in shock."
Sports stars from Las Vegas and across the United States were stunned and saddened Monday at the tragedy.
"Sad day. Love and prayers #lasvegas. Let's not let hate win. Be kind to one another," wrote former heavyweight boxing champion Mike Tyson, who lives in Las Vegas.
"Speechless, pray for my home," US 2016 Olympics high jumper Vashti Cunningham wrote on Twitter.
"The pride of Vegas runs deep when you are born and raised in such a great town. I can't fathom the horrific event that has taken place!" tweeted Washington Nationals outfielder Bryce Harper.
"My thoughts and prayers go out to the families that have been affected by this and to all the people that have lost their lives way too soon! Las Vegas I love you and stand with you."
Tennessee Titans running back DeMarco Murray was a three-sport high school star in Las Vegas and stunned by the incident following his club's 57-14 NFL loss at Houston.
"Terrible news coming out of my hometown, praying for all affected by this horrific situation," Murray said. "My thoughts are with the victims and their families."
US stock car auto racer Kyle Busch, second in the championship chase as the season winds down, was also struggling with the Vegas slayings.
"Devastated to hear of the senseless tragedy in my hometown," he tweeted. "My thoughts and prayers are with all of you."
The National Hockey League's first-year Vegas Golden Knights, the city's first major US sports league team set to open their inaugural season Friday, tweeted support for first responders and condolences to the victims.
"We extend our thoughts, prayers and heartfelt condolences to the victims, their families and all those affected by the tragic events that took place on the Las Vegas Strip Sunday night," the team tweeted.
"We are grateful for our city's brave first responders, law enforcement and medical personnel and the courage they demonstrated under unimaginable circumstances. We join in our city's mourning and offer our full support to the people of Las Vegas to help grieve, heal and persevere."
The NFL's Oakland Raiders, set to move to Las Vegas for the 2020 season, sent out a statement about their future home, saying, "The Raiders family is shocked and saddened by the tragedy in Las Vegas and our thoughts and prayers are with the victims, families and first responders. The heart of the Raider Nation goes out to Las Vegas."
NBA superstar LeBron James of the Cleveland Cavaliers expressed his shock as well, tweeting, "Pray for Vegas!! What the hell is going on people!?!? My prayers sent to the heavens above for all the families."
University of Nevada Las Vegas ice hockey assistant coach Nick Robone was among those shot at the concert, according to the team's twitter page. He suffered a bruised lung and was in intensive care following surgery but is expected to make a full recovery after being hospitalized indefinitely.
The reigning Super Bowl champion New England Patriots tweeted "our hearts are with everyone affected by last night's tragedy in Las Vegas" while the reigning World Series baseball champion Chicago Cubs tweeted, "We are deeply saddened by the tragic shooting in Las Vegas."

Source: AFP