RANCHO CUCAMONGA, Calif. — A Southern California woman is fighting for justice after her 10-year-old son Nathanial died from exposure to fentanyl.

Not only does Marcy Castro think the person who did it should be charged with murder, but she’s advocating for tougher punishments for those responsible.

“I want justice for my son, and I won’t stop until he gets it, because he deserves it,” she said in an interview with our sister station, ABC7 Eyewitness News in Los Angeles.

It happened on Dec. 12, 2024, at their home in Rancho Cucamonga. Castro said she got a phone call from a family member informing her that Nathanial had stopped breathing.

“I couldn’t even comprehend what he was saying,” she said. “I could hear 911 in the background, and he says to the paramedics what do I tell her, and they say he was pronounced dead.”

At first, Castro said they didn’t know what caused her son’s death. But weeks later she received a phone call from the coroner’s office informing her that Nathanial’s death was caused by fentanyl.

“We were just shocked as to how this could have happened, and how this was exposed to my son,” said Castro. “We’re a drug-free home.”

Or so they thought.

After detectives with the San Bernardino County Sheriff’s Department investigated the case, they arrested Castro’s brother’s girlfriend, Christina Alvarez, who was living at the home. Castro said Alvarez was the one who prepared Nathanial’s dinner the night before his death.

“She gave him shrimp that night for dinner, so we believe it was something he ingested, maybe she touched something,” Castro said. “Detectives came down and said they were arresting her. The district attorney wanted to press charges because of the severity of the case, and then they found more fentanyl on her.”

Alvarez was charged with felony child endangerment and is awaiting a mental disorder diversion hearing later this month.

“She should be charged with murder,” said Castro. “My son was murdered because of her reckless actions.”

Castro said she’s started a campaign, called Nathanial’s Light, which has gathered more than 1,200 signatures and is in the process of contacting lawmakers to demand action.

“(Nathanial) didn’t go out looking for the drug; he didn’t go out looking for a high, he was just an innocent boy in his home,” she said. “I want justice for my son, and I won’t stop until he gets it.”