A family in New Jersey, trapped over the weekend in the massive East Coast snowstorm, was trying to dig its way out when the chill became too much to handle. The mother and her children — ages 1 and 3 — huddled in the car with the engine running to keep warm. The kids’ father tried to clear the snow outside.

Authorities said no one seemed to realize that the tailpipe was clogged with snow, pushing deadly carbon monoxide gas into the car. When the father went to check on them, police said, he could not wake them up.

The father, Felix Bonilla, started “crying and jumping,” Isabel Carmona, a neighbor, told NBC New York.

Bonilla called 911. Neighbors tried to help, performing CPR until paramedics arrived, according to news reports. But, police said, when EMTs got there, they could not find a pulse for the mother or her son.

Police said the 3-year-old girl was rushed to St. Joseph’s Regional Medical Center in Paterson, N.J. Passaic Mayor Alex Blanco later told NorthJersey.com that the little girl was “fighting for her life.”

“The paramedic, he cry, and the police cry; everybody cry,” Carmona, the neighbor, told NBC New York.

The mother, identified by neighbors as 23-year-old Sashalynn Rosa, and her 1-year-old son, Messiah, were killed, authorities told NorthJersey.com. Three-year-old Saniyah was listed in critical condition.

“The doctors say they don’t think she’s going to make it; doctor says she has a slight chance to make it,” the kids’ grandfather, also named Felix Bonilla, told ABC affiliate WABC, adding: “It’s hard to lose them like that.”

Carbon monoxide has been called the “silent killer,” a colorless, odorless, tasteless — and toxic — gas that causes people to lose consciousness in minutes. From 1999 through 2010, more than 5,100 people died from accidental carbon monoxide poisoning in the United States, according to the Centers for Disease Control and Prevention.

“It’s heartbreaking, it’s something you can’t foresee,” Blanco, the mayor, said Sunday from the scene, according to NorthJersey.com. “It’s something that is not on ‘the list’ of things not to do during a storm. We’ll all have to add that to the list. Something like this, I probably would have made the same mistake.”

Passaic police said the incident should serve as a warning for others, especially during the winter season.

“Any snow that covers your tailpipe you want to shovel the snow from the back of the car and clear the tailpipe before you even start the car,” Battalion Chief Chris DiBella told WABC.

Numerous municipalities and police departments in New Jersey have released safety guidelines from the Rutgers Poison Information and Education System to help people avoid carbon monoxide poisoning.

One precaution: “Remove snow from car exhaust pipe before sitting in car and letting it warm up. Failure to remove snow can result in carbon monoxide poisoning. Be sure there is ample room for air to circulate in front and behind your car to allow any exhaust to dissipate and not build up around your car.”

The recent snowstorm was responsible for more than two dozen deaths, according to the Associated Press.

A Pennsylvania man, 56-year-old David Perrotto, died in a separate snow-related incident over the weekend when, police said, he was sitting in a running car as a passing plow buried it in snow.

Berks County Assistant Chief Deputy Coroner John Hollenbach told CBS Philly that Perrotto had apparently been trying to dig his car out of the snow. Hollenbach said investigators believe Perrotto got inside the vehicle — which was running — either because he needed to rest or was trying to evade the plow.

When the snow buried the car, Hollenbach said, it clogged his exhaust pipe and kept him from escaping.

Bonilla, who lost his family to carbon monoxide poisoning, is paralyzed by shock, his family said.

“I can’t even express how I feel right now; I got no words,” the children’s paternal grandfather told NBC New York. “My son, he can’t even say nothing, he can’t even move, he can’t even talk.”

This story has been updated.