Gunman Omar Mateen is responsible for killing 50 people and injuring 53 more at a gay night club in Florida early Sunday morning.
He had been trained as a security guard, and legally had his weapon. Orlando, Fla. police shot and killed him after the attack.
Orlando authorities are considering this an act of domestic terror, as it is the worst attack since September 11, 2001.
U.S. officials revealed that the 29-year-old called 911, pledged allegiance to ISIS and mentioned the Boston bombers during the shooting as well.
His father, Mir Seddique, later spoke to USA Today
, saying, "I don't know why he did it. He is dead, so I can't ask him. I wish I knew."
"I apologize for what my son did," he said to NBC News
. "We are saying we are apologizing for the whole incident. We weren't aware of any action he is taking. We are in shock like the whole country." He later revealed that the attack may have been premeditated from his anger over seeing two men kiss months prior.
President Barack Obama addressed the fatal shooting.
Now, celebrities are taking to social media to react to the devastating news.
Cyndi Lauper took to her Twitter to express her opinion.
Julie Bowen took the opportunity to wish today's LA Pride participants safety.
also mentioned LA pride in the aftermath of the Orlando shooting.
Sabrina Carpenter also kept her opinion brief.
Countless celebrities, including Khloe Kardashian
, shared the same photo to honor Orlando on Instagram.