Capitol Police Officer Brian Sicknick died following the Capitol insurrection last month.
Officials are still investigating his death and looking for suspects.
Investigators told CNN that Sicknick may have been fatally hit with bear spray during the riot.
Related: New Capitol riot footage in first days of impeachment trial
Federal authorities are investigating the death of US Capitol Police Officer Brian Sicknick, who died following the January 6 insurrection, and one leading theory is that bear spray is to blame.
The investigation into Sicknick's death is still ongoing, and Metropolitan Police Department Chief Robert J. Contee III said at a news conference last week that police are looking through video and audio evidence for clues into what and who killed the Capitol Police officer.
Last month Capitol Police said Sicknick died one day after he was "injured while physically engaging with protestors."
Investigators told CNN this week that they're narrowing down a list of suspects in Sicknick's death, and said a leading theory is that the police officer was hit with bear spray.
According to CNN, Sicknick may have been fatally hit bear spray or another chemical irritant being spread by rioters during the insurrection.
This isn't the first time bear spray has been brought up in connection to the riot.
Christina Laury, an officer with the Metropolitan Police Department in Washington, DC, previously told WJLA that when she arrived on scene at the riot, other officers were doing everything they could to keep rioters from accessing the building, even as they were being sprayed with chemical irritants.
"By the time I got there, officers were already getting, you know, sprayed with whatever these individuals had, which I believe they had bear mace, which is literally used for bears," she said.
Bear spray was also brought up in former President Donald Trump's Senate impeachment trial on Wednesday.
In audio from the Capitol riot played at the trial, police officers can be heard screaming that the insurrectionists were spraying them with bear spray, CNN reported.
Republican Sen. Mitt Romney later told reporters that Capitol Police Officer Eugene Goodman told him that he "had to breathe a lot of bear spray and tear gas and that he was nauseated" during the riot.
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