At the time of his death in May, the 5-year-old weighed just 19 pounds — less than half the weight of an average boy his age.

The cause of death was a drug overdose.

Specifically, officials said this week, the sickly boy died after his parents medicated him with OxyContin.

Charles Burks, 45, and Jennifer Burks, 40, of Endicott, N.Y., are facing second-degree manslaughter charges for their son’s death. Investigators believe the couple gave the boy crushed OxyContin, a highly addictive prescription opioid painkiller that ultimately killed him.

Broome County District Attorney Steve Cornwell told The Washington Post that the boy was in need of specialized care and had developmental and medical problems. His parents, Cornwell said, “took it upon themselves to self-medicate the child.”

“It’s alleged that the parents failed to get the proper treatment for the child in a timely manner,” Cornwell said. The prosecutor declined to elaborate on what kind of medical problems the child had, other than saying he was severely underweight.

Police responded to the couple’s house on May 7 after receiving a medical call, Endicott Police Chief Patrick Garey told The Post. The boy was then taken to the hospital.

Officials shared few details about what happened next, other than to say that the couple abruptly left New York within a month of their son’s death, traveling to North Carolina, where they lived at a campsite.

Investigators received a tip from a police officer at the New Hanover Regional Medical Center in Wilmington, N.C., that Charles and Jennifer Burks visited someone at the hospital, Cornwell said. The Burks later drove back to New York for an unrelated matter, Cornwell said, and were arrested and arraigned Thursday.

Officials did not say whether the boy was still alive when he was taken to the hospital in May. It also remains unclear whether his parents were at home when police were called, or whether one or both of them had prescriptions for OxyContin.

As is customary in Broome County, the case will be heard by a grand jury, which will then decide on the appropriate charges. The charges may be different or the same as the original manslaughter charges, the prosecutor said.

A second-degree manslaughter charge is punishable by up to 15 years in prison.

Cornwell said the couple has other children, though all of them are adults. He declined to say whether they have a history with Child Protective Services.

Records, however, show that Charles Burks is registered as a sex offender in New York and North Carolina. He was convicted of third-degree rape of a 15-year-old girl in 1998 in Broome County.

As previously reported by The Post, deaths from prescription opioids and heroin hit record levels in 2014. The Centers for Disease Control and Prevention said in December that 47,055 people died of drug overdoses that year – up from 16,849 in 1999.

More than half of the 2014 deaths resulted from prescription opioid and heroin overdoses, according to the CDC.