The collapse occurred around 6:50 a.m. Monday on the 1800 block of South Broad Street, near Joseph Street, in Hamilton Township, Mercer County.
The victim who was killed was identified as a 38-year-old Tika Justice. Her daughters, a 16-year-old and a 20-year-old, survived and are now hospitalized.
The 20-year-old was found chest-deep in debris when first responders arrived, while the 16-year-old was found with her mother's body.
James Feig was the first one at the scene.
"I rode up to it, went back behind the billboard, and there was a lady buried in the rubble," Feig said. "She had the phone in her hand. She was talking to dispatch."
Feig said they tried to call out to others who were trapped.
"No response, so they either couldn't hear us or were unconscious," he said. "Soon as I saw the fire truck come up the road, I told her, 'Here comes the fire truck. Hold on.' It brought tears to my eyes."
Feig stayed at the scene and attempted to comfort the 20-year-old woman who was partially buried until first reponsders could dig her out.
"She was doing well, and that's what you want to see," witness Casey Teuchert said. "And I was just so happy at that point just to see somebody come out of there."
PSEG was on scene to shut off gas lines, which is standard procedure for these types of incidents.
Mercer County, NJ 3-story home collapses this morning with at least 3 residents inside. @PSEGNews is on scene to shut off gas as is standard procedure. No word on injuries or cause of collapse yet. @6abc pic.twitter.com/hf0Ka0SjvY— Jeannette Reyes (@6abcJeannette) July 23, 2018
The cause of the collapse has not been determined at this time and remains under investigation.
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