(CNN) -- Some thought it was a bomb. Others thought it was the commuter train that runs behind their buildings jumping the tracks. 

It shook upper Manhattan for blocks -- and when it was over, a five-story apartment building and its neighbor were gone. 

After Wednesday morning's deadly building explosion in East Harlem, squads of firefighters dug through piles of shattered bricks and beams. Ladder trucks sprayed water into the gap where the buildings once stood. As Detective Martin Speechly, a New York police spokesman, put it: "1644 Park Avenue appears not to be there anymore." 

Along with that five-story apartment building, with a Latino evangelical church on the first floor, a neighboring piano store and the four floors above it collapsed in the blast. 

One nearby resident, Angelica Avila, told CNN she was trapped in her apartment down the block for a short time afterward. Her stepmother had to sneak in through the back to try and open the door for her, she said. 

"My neighbors came banging on my door. I guess they were evacuating the building, and I couldn't get out -- my door was jammed," she said. "Everything off my windowsill fell, and I guess the impact of the explosion jammed the door as well." 

Something similar happened to Aisha Watts, who had just returned to her apartment in one of the adjoining buildings after taking her children to school. Then the windows broke out, and "the walls came tumbling down," Watts said. 

A neighbor helped her out of her apartment, because the door was stuck in its frame. And she and her neighbors will have to find someplace else to stay temporarily. 
What did it house on its first floor?
with a Latino evangelical church on the first floor