Celebrities took to social media to respond to the explosion at an Ariana Grande concert in Manchester on Monday that left 22 people dead and dozens of others injured.
Multiple law enforcement agencies joined the UK police to investigate the incident, who are treating it as a "terrorist incident."
Grande tweeted a short message to her fans after the tragedy saying her heart was "broken" and she was "so, so sorry."
Her rep confirmed earlier the star was "okay," adding that "we are further investigating what happened."
Her fellow celebrities shared their thoughts and concerns as the news unfolded.