A 13-year-old boy fatally shot by Columbus, Ohio, police last week was “more likely than not” running away from an officer at the time he was killed, according to an independent medical examiner retained by the child’s family.

Attorneys for the family of Tyre King said on Monday that the local coroner’s office completed its autopsy of the child’s body, but the results wouldn’t be made available for at least six weeks. In response to the delay, the attorneys said, Tyre’s family decided to hire an independent forensic pathologist from Michigan to evaluate the number, characteristics and location of the gunshot wounds on Tyre.

“Based on the location and the direction of the wound paths it is more likely than not that Tyre King was in the process of running away from the shooter or shooters when he suffered all three gunshot wounds,” the examiner, Dr Francisco Diaz, said, according to a statement from the family. Co-attorney Sean Walton told the Guardian in an email that Diaz conducted his examination of Tyre’s body on Sunday. The attorneys didn’t immediately respond to a request for a copy of Diaz’s report.

Tyre was killed last Wednesday at 7.42pm, when authorities responded to a report of an armed robbery of $10 by a group of teenagers. When officers arrived, Tyre was spotted with two other males who matched a description of the suspects and soon fled on foot. As officer Bryan Mason approached King, police said the child removed a BB gun from his waistband, before he was shot “multiple” times. Tyre was transferred to a hospital and pronounced dead at 8.22pm.

Mason, a nine-year veteran of the Columbus police division, has since been placed on administrative leave and will receive psychological counseling. Authorities have said Tyre’s BB gun resembled a real firearm, and the police division’s chief Kim Jacobs said her officers “carry a gun that looks practically identical to this weapon”.

Diaz found that Tyre, who the examiner noted was 5ft tall and weighed less than 100lbs, died from three gunshot wounds, “any of which could be determined to have been cause of death”, according to the family’s statement. The wounds were found on his temple, collarbone and the left flank, the statement said.

Diaz is an assistant professor of pathology at the University of Michigan in Ann Arbor, according to his LinkedIn page, and since 2001 he has worked as a medical examiner in Wayne County, Michigan. Diaz didn’t didn’t immediately respond to a request for comment. Tia Moretti, public information officer for the Franklin County coroner’s office, confirmed results of Tyre’s cause of death and manner are pending, as toxicology tests won’t be completed for at least six weeks.

Columbus police on Saturday also said Tyre’s friend, Demetrius Braxton, was arrested in connection with the robbery that preceded the shooting. Braxton, 19, was charged with one count of robbery, a second-degree felony. Last week, he told the Columbus Dispatch that Tyre wanted to rob someone for money, and that he was with him at the time of the shooting.

“The cops said to get down,” Braxton told the newspaper. “We got down, but my friend got up and ran … [and] when he ran, the cop shot him.” Police claimed in court documents that Braxton was armed with “what appeared to be a black semi-automatic handgun”, according to the ABC affiliate in Columbus, and that he was involved in the robbery of a man for $10. Braxton was expected to be arraigned on Monday.

Attorneys for Tyre’s family declined a request by the Guardian on Sunday for an interview. In the statement, the family asked the public to “continue to withhold final judgment until all the facts are known and vetted”. The family reiterated its request for an independent investigation and called upon the Columbus police division and Franklin County prosecutor’s office, which has jurisdiction over the city, to be removed from the current probe of Tyre’s death.

“The Columbus police department, the City of Columbus and most importantly Tyre King and his family deserve the benefit of an investigation from a law enforcement agency that has no direct impact from the outcome of that investigation,” the statement said.