"So many people were hurt," 29-year-old Antonio tells PEOPLE
Credit: Splash News Online

As people fled from a gunman inside a popular gay nightclub in Orlando, Florida, early Sunday – during the deadliest mass shooting in modern American history – witnesses tells PEOPLE it was the “craziest thing.”

“So many people were hurt,” says 29-year-old Antonio (no last name was given).

“Me and my friends were out in the parking lot. We were just leaving,” he says. “We heard this sound that I thought was the beat of the music inside. And then people started running out the front door. All hell broke loose.”

Carmen Pena, 30, tells PEOPLE she was inside the club, in the same room with the shooter, when he started firing.

“I know that he was in the room, because I heard a woman screaming, and then all of a sudden she stopped,” Pena says. “The gunshots were so loud. It felt like they were right next to my ears. Every second, I thought I was going to be hit.”

Pena says that as soon as she heard a shot, she knew what it was and “got down on my hand and knees.”

“There were so many people running around, and I was trying to get to the back door. And I knew the shooting was behind me, but I was afraid to turn and look,” she says. “So it was like tunnel vision looking at the door. I was praying to all the saints to keep me safe.”

Along with the screams outside the club, Antonio says he saw one woman “who was holding her shoulder and her hand was covered in blood, she wasn’t screaming or making any noise, just walking out staring straight ahead,” as another woman helped her walk.

He says he saw a man stepped on as he tripped and fell. And he says he saw a man who had run outside stop and scream back at the door, “Michael! Michael!”

Outside the club, the victims tended to one another, Antonio says.

“A guy walked past and said, ‘Help, help. I think I’ve been shot,’ ” he says. “These other guys ran up and tried to stop the bleeding. They were putting their clothes on it to stop the bleeding.

“People were taking off their shirts and using them to stop the bleeding.”

And in the parking lot, Antonio says, “a guy was lying on the ground and two women were kneeling over him, telling him, ‘Stay with me. Stay with me.’ ”

“I can’t stop crying,” Pena says. “I feel so sick. It was awful.”

Hours later, the Islamic State claimed responsibility for the attack, Reuters reports. In a Sunday afternoon news conference, U.S. Sens. Bill Nelson and Marco Rubio also laid blame with ISIS.

Authorities have not yet announced a motive for the shooting, which they say killed at least 49 people and hospitalized at least 53.

The suspect, reportedly identified as Omar Saddiqui Mateen, was killed in an exchange of gunfire with police.