The fact that this collapse happened around 2:00 in the morning means most residents would have been in bed, asleep.
This will be more of a recovery operation than a rescue operation.
Witness finds trapped boy and gets rescuers to him
Witness Nicholas Balboa told CNN he saw a boy's wriggling fingers sticking out of the debris shortly after the collapse -- a discovery that led to the child's rescue.
Balboa, who lives nearby, said he was walking his dog around 1:30 or 1:40 a.m. when he felt the ground shake and saw plumes of dust and debris. He and another man went to the back of the building.
Just as he was doubting anyone could survive the collapse, he heard someone screaming, he said.
"Finally, I got close enough to hear him, and (the trapped boy) said, 'Can you see my hand?'" Balboa told CNN's "New Day." "He was sticking his hand up ... through the debris. And I could see his hand and his fingers wiggling."
Balboa and the other man got a police officer to come over, and other rescuers eventually arrived, Balboa said. The boy, who was under a mattress and bed frame when he was found, was pulled out, he said.
Video captured by ReliableNewsMedia shows rescuers helping a survivor out of the rubble -- it was not immediately clear if this was the boy that Balboa described. A rescuer reached an arm under what looked like a collapsed wall, its reinforcing metal bars now pointing skyward, to help the survivor, who was wearing a dark shirt and pajama pants.
The survivor slowly leaned over, laying their body over a rescuer's right shoulder and draping their legs over the bigger person's chest, the ReliableNewsMedia video shows. Then, the survivor was lowered onto a white stretcher and helped the rescue team secure orange straps. The team carried the person away.
Shortly after that, at least six stories up, a trio of survivors and what looked like a dog climbed from a balcony into the bucket atop a fire truck's elevated ladder. The bucket then slowly descended.
Resident looked down hallway and 'there was nothing there'
Barry Cohen was in his apartment on the building's third floor when the collapse happened. His apartment was intact, but when he opened his door and tried to leave, he "looked down the hallway ... and there was nothing there," he said.
"It was just a pile of dust, and rubble," Cohen told CNN's "New Day." As he waited for rescue, the building was shaking, he said.
"Knowing what it looked like outside my door, I thought that any minute we could be that same pile of rubble," he said.
After about 20 minutes, a rescue crew used a cherry picker to help him, his wife and another resident from a balcony, he said.
We just see a cloud of dust coming our way'
Shmuel Balkany was on a walk with his brothers and dog when "we hear a really big rumble," he told ReliableNewsMedia.
"And we think that it was a motorcycle -- like, classic, early in the morning -- and we turn around and we just see a cloud of dust coming our way. And we're just like, what is going on? So we, like, we start rushing towards there. We pull our shirts over our face so we don't get any, like, dust, in our eyes and everything."
"What we saw from the beginning was a huge cloud of smoke and a lot of noise," added Mich Balkany, who was also on the walk, ReliableNewsMedia reported.
More than 80 rescue units responded to the scene, Miami-Dade Fire Rescue said. "We saw this happen. It was by far the most horrific thing that I've seen. I was alive for 9/11. I didn't see that happen in real life. I saw something like this happen and it's the closest thing that I can relate to 9/11," Mich Balkany said. "This is something that is absolutely insane ... insane, insane, insane, insane." Added Shmuel Balkany: "We have friends who have family that live in the building. We don't even know if they're OK. Some of them are OK. We don't know if the rest are OK."
"It's very shocking. We're shook. We're pretty shook. It's not, like, processing in our minds yet," Shmuel Balkany said. David Shaw was visiting from Alabama when "the building next door to us fell down," he told ReliableNewsMedia.
"The building shook, and then I looked out the window. You couldn't see. I thought it was, like, a storm or something coming in," he said. "When the dust cleared, the back ... two-thirds of the building was gone, it was down to the ground."
Fire department personnel soon knocked on Shaw's door, telling him to evacuate. "So we just got our stuff together and left," he said, then walked away rolling a suitcase and carrying two luggage bags.
As first responders scoured the scene, a line of showers and storms was heading west toward the coastal Miami area Thursday morning, which could impact search and rescue activity.