JERSEY CITY, N.J. (CBSNewYork/AP) — Investigators are trying to determine what happened to a mother and her 5-year-old son who died after being found unconscious in their Jersey City apartment.

It’s unclear who made the initial call to police, but the woman, said to be in her 20s, and her child were found unconscious in their home at 34 Lincoln St. around 6:30 p.m. Wednesday. They were pronounced dead at Christ Hospital.

Officials said the deaths are being investigated as suspicious.

Francisco Ventura only learned of his grandson’s death Thursday morning when he came to visit the boy and his mom.

“Oh my God! What happened, mami?” he asked CBS2’s Janelle Burrell.

Investigators later took the shaken grandfather away.

One nearby resident described the scene Wednesday night. “I see a lot of police and a lot of people looking, and they’re talking about somebody die over there,” neighbor Emma Herrara told CBS2’s Janelle Burrell. “I feel bad because I live over here, and I never see that on this block.”

Neighbors said the family has lived in the apartment for about a year. They said the deaths are sad and shocking.

“Because it’s a very quiet neighborhood. Very nice, quiet neighborhood,” one man told WCBS 880’s Levon Putney.

“It’s a sad, sad story because I know I have seen the mother and the child going to school and going for shopping and all those things,” another neighbor told Burrell. “It’s a sad story.”

Fire officials tested the air quality in the home and say that all tests so far have come back negative for carbon monoxide. The apartment has been sealed.

The Hudson County Prosecutor’s Office is investigating the deaths.

The names of the victims have not been released.

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