America has witnessed the worst mass shooting in its history at a gay nightclub in Orlando. People are grief-stricken and struggling to believe that it has really happened. Fifty people have died and 53 others are injured in the Orlando nightclub mass shooting.

An American who pledged allegiance to ISIS carried out the massacre, which has been considered as the nation’s worst attack since 9/11. Investigators previously came across the man back in 2013, when he attacked another gay dance club. An FBI special agent said that law enforcement agents first spoke to Omar Mateen, the assailant, when he made “inflammatory comments” which were considered as radical but “could not verify the substance of that comment,” as per Ft.com.

The very next year, Mateen again came under authorities’ radar after his ties to Moner Mohammad Abu-Salha were revealed. Moner Mohammad is the first known suicide bomber of America who died in Syria. FBI special agent Ron Hopper said that they again interrogated him and found that his connection with Moner Mohammad was minimal.

Mateen was equipped with an assault rifle and pistol when he carried out the shooting at about 2:00 a.m. on Sunday. Police said that he killed at least 50 people and injured 53. In between the shooting, he called 911 and pledged allegiance to ISIS and also mentioned Boston Marathon bombers, reported CNN. Police entered the club in an armored vehicle and killed the assailant.

Orlando Police Chief John Mina said that one officer was injured in the shooting when a bullet fired by the assailant struck the officer’s helmet. He was wounded in his face.

Although no terrorist organization has claimed responsibility for the massacre, ISIS sympathizers have reacted by praising the attack.

President Obama in his address to the nation offered his condolences to Orlando nightclub mass shooting victims and said, “We know enough to say this was an act of terror and act of hate. This is an especially heartbreaking day for our friends who are lesbian, gay, bisexual or transgender.”

Obama also said that the FBI is investigating the Orlando nightclub mass shooting, which he called as  “an act of terror and an act of hate.” He further commented that Mateen “was a person filled with hatred.”

Mohammad Musri, an imam from Florida and president of American Islam, said that the attack would worsen the relationship between Muslims and rest of the population. “They had already been deteriorating after Paris and Brussels and San Bernardino and we have been receiving threats today, a lot of nasty calls, emails, Facebook posts, and tweets,” he said.

“We need to redouble our efforts to defend our country from threats at home and abroad,” Democratic presidential nominee Hillary Clinton said.