Story highlights A 3-year-old Russian boy adopted by a Texas couple died in January

A Russian official has slammed U.S. authorities' handling of the case

A Texas investigator found more than 30 cuts, bruises, other marks on the dead boy

The adoptive parents said the boy frequently hurt himself, a new document states

A 3-year-old adopted boy -- whose death in West Texas has drawn stern criticism from Russia -- had more than 30 bruises, cuts and other marks on his body soon after he was pronounced dead, according to a report from a Texas medical examiner obtained by CNN.

Along with his 2-year-old brother, Max Shatto arrived in the United States with his adoptive parents in November 2012. Just more than two months later, his adoptive mother told authorities that she found him unresponsive in the family's Gardendale, Texas, backyard. He was pronounced dead shortly after arriving at a nearby hospital.

Soon after Max's death on January 21, Russia's top child rights advocate tweeted that the boy had been "killed" or "murdered." Children's Rights Commissioner Pavel Astakhov later acknowledged he might have spoken too soon -- though he has remained highly critical of the U.S. handling of the case.

The documents were obtained Thursday from the medical examiner's offices for Ector County and Tarrant County. They offered more details from the account by Laura and Alan Shatto about the boy's time in America as well as the condition of his body at the time of his death.

Russia's consul general in Houston has received the report, said Yevgeniy Khorishko, a spokesman with Russia's embassy in Washington. Russian officials will review the findings, but until then they have no comment.

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An investigator with the Ector County office who examined Max's body externally soon after his death documented 31 bruises, abrasions, scratches and other issues from head-to-toe, according to the death investigative report.

Both parents in the report claimed that the boy -- who they and a doctor said was born to an alcoholic mother -- would try to hurt himself in various ways.

"They stated that (Max) was displaying behaviors such as banging his head on the bathtub, throwing himself down, holding his breath and clawing himself," wrote investigator Sondra Woolf.

A Denton, Texas, doctor told authorities that after examining the child's deteriorating condition during a second visit and listening to the parents' accounts, he prescribed the boy Risperidone, an antipsychotic medication. The Shattoes said they first gave Max the drug on January 15 but stopped on January 18, concerned it was affecting his ability to swallow, the report said.

Laura Shatto told authorities that she last saw Max outside, believing he was about to go on a slide, just before she went inside to use the bathroom. She came out to find him prone on the ground, and she called his name and shook him vigorously before calling 911.

The documents also included a preliminary autopsy report conducted by the Tarrant County Medical Examiner's Office, completed on January 23.

Medical Examiner Lloyd White wrote to his colleagues in Ector County, "Based on the findings at this point, I suggest laceration of small bowel mesentry due to blunt trauma to (the) abdomen as the cause of death. I'll leave the manner of death up to you pending investigation.

"On the whole, there appears to be a strong likelihood that this death was accidental, probably the consequence of a fall from playground equipment in his yard."

The Ector County medical examiner later concluded that Max Shatto's death was accidental , finding that the bruises and other issues were consistent with a "self-inflicted" injury, District Attorney Bobby Bland said March 1.

Astakhov had accused the adoptive mother of killing the boy and giving him "psychotropic substances," Russia's state-run RIA Novosti news agency reported.

But toxicology reports came back negative, and there were no substances found that could have contributed to the child's death.

Soon after the news came out that Max's death had been deemed accidental, Russia's Foreign Ministry expressed concerns and noted it did not receive the information from U.S. officials but rather from the media. It asked the United States to give Russian consular representatives the relevant forensic documents, including a death certificate.

A few weeks later, Astakhov again slammed Texas authorities -- this time after they decided not to charge the adoptive parents.

Bland announced March 18 that a grand jury had declined to indict Laura and Alan Shatto, adding that they'd found no evidence to charge the people and stating the boy died of a "tragic accident."

The Russian child rights advocate responded to that development with a tweet, reported by a RIA Novosti, claiming the district attorney hadn't done enough to the investigate the death of the boy also known as Maxim Kuzmin.

"The Texas prosecutors' position in the case of Maxim Kuzmin is upsetting because they refused to scrutinize the circumstances of his death," Astakhov wrote.

The boy's death aggravated U.S. State Department efforts to push through more than 500 adoption cases in which American families have already begun the process to adopt a Russian child before Moscow in December passed a law banning adoptions of Russian children by Americans.

That law bans adoptions by Americans ostensibly because of documented cases of abuse by adoptive parents. But others say the Russian move is in retaliation for a U.S. law that places restrictions on Russian human rights abusers.

Americans adopted close to 1,000 Russian children last year, according to State Department figures.

Though the number has dropped in recent years, Russia remains the third-most popular foreign country after China and Ethiopia for U.S. foreign adoptions.