“Everyone get out of pulse and keep running.”

Minutes after a gunman opened fire inside the Pulse nightclub in Orlando early Sunday morning, killing at least 50 people and wounding 53, someone managed to post this chilling message on the bar’s Facebook page.

The message was posted about 2:30 a.m. as details of the worst mass shooting in American history began to emerge and has since been shared almost 10,500 times, garnering 26,000 reactions and more than 3,900 comments.

Thousands of Facebook users from around the world commented on the post to express their condolences. Many even changed their Facebook profile pictures to the Pulse logo with a rainbow running across the bottom and a ribbon commemorating the victims at the top.

Other users, who said they were in the club at the time of the shooting, provided more information about the assault.

Early Sunday morning, Facebook user Ricardo J. Negron Almodovar wrote: “I was there. Shooter opened fire around 2 a.m. People on the dance floor and bar got down on the floor and some of us who were near the bar and back exit managed to go out through the outdoor area and just ran.”

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Many people monitored the Facebook post hoping to learn the status of friends and family.

About 3 a.m., Lilbia Carmen wrote: “Nothing yet. My daughter is in there. Please keep praying for them … She’s waiting for the cops to be able to come out. I was on the ... [phone] and all I hear is shot guns.”

More than 500 people responded to Carmen, offering their support. Carmen later posted a photo of herself embracing her daughter after she had returned home safely.

Sunday afternoon Facebook activated its Safety Check feature, which was first launched last year following the Nepal earthquake. The feature allows users of the social network to see whether their friends and family in the Orlando area are safe.