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A father and his seven children found dead inside a Maryland home were poisoned by carbon monoxide from a generator they were using because they could not keep up with their electricity bills, relatives and a friend said.

Rodney Todd Sr., 36, and his seven kids, ages 6 to 16, were found by officers in the southern Maryland peninsula town of Princess Anne on Monday, police said.

Todd's mother and stepfather, Bonnie and Lloyd Edwards, told The Associated Press that a utility firm had cut off his electricity because of an outstanding bill.

"To keep his seven children warm, [Todd] bought a generator," Lloyd Edwards told the AP. "It went out, and the carbon monoxide consumed them."

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The couple added that police had informed them the family was killed by carbon monoxide poisoning. Officials told NBC News the official cause of death was pending a medical examiner's report Tuesday.

Family friend Stephanie Wells also told NBC News that the family’s power had been shut off because of an unpaid bill. "I just feel that the system failed him," Wells said. "They didn't reach out to help him with his utility bills."

Delmarva Power, a utility firm covering Maryland and Delaware, told NBC News it was investigating the incident.

Princess Anne Police Chief Scott Keller confirmed officers found a generator inside the home that had run out of fuel.

Todd's mother said her son was a hard-working and devoted father to his children, of whom he'd had custody for about three years.

"My son was a good son," said Bonnie Edwards, who was also the children's grandmother. "Not only was he my son — that was my friend. I could call and talk to my son about anything."

"You couldn't ask for a better father. You couldn't ask for a better man," she added.

NBC News' Alexander Smith and The Associated Press contributed to this report.