Washington's chief medical examiner has determined that U.S. Capitol Police Officer Brian Sicknick died of natural causes the day after the riot on Jan. 6 after he suffered two strokes.
The autopsy revealed that Sicknick, 42, said the strokes at the base of the brain stem were caused by a blood clot, Chief Medical Examiner Francisco Diaz said.
The formal finding was that the death was caused by "acute brainstem and cerebellar infarcts due to acute basilar artery thrombosis" and that the manner of death was "natural."
Diaz told The Washington Post that the autopsy found no evidence that Sicknick experienced an allergic reaction to chemical irritants. He also said there was no evidence of either external or internal injuries.
"All that transpired played a role in his condition," Diaz told the newspaper.
Capitol Police have said that Sicknick returned to his office after the riot and collapsed and that he died at a hospital about eight hours later.
The findings will make it difficult to charge any of the rioters with causing Sicknick's death, and no such charges have been filed. Two men, Julian Khater of Pennsylvania and George Tanios of West Virginia, were arrested in mid-March and accused of assaulting Sicknick with bear spray.
Sicknick was honored in a ceremony at the Capitol and buried at Arlington National Cemetery. His family said, "Brian is a hero and that is what we would like people to remember."
In a statement, Capitol Police said they accepted the findings. "But this does not change the fact Officer Brian Sicknick died in the Line of Duty, courageously defending Congress and the Capitol.
"The Department continues to mourn the loss of our beloved colleague. The attack on our officers, including Brian, was an attack on our democracy," the statement said.