Investigators focus on whether chemical irritant played role in Capitol Police officer's death

Investigators are looking closely at video evidence of the Jan. 6 Capitol assault that appears to show at least one suspect spraying what appears to be a chemical irritant at police officers in the Capitol and the possibility that Officer Brian Sicknick may have been among those officers, law enforcement sources told ABC News.

Sources say while significant gaps remain in the investigation, they are working to determine if there is evidence of a possible assault on Sicknick and whether such an assault had anything to do with the medical distress that led to his death.

There were several chemical irritants dispersed at the Capitol during the assault, including bear spray, mace, pepper spray and fire suppressing chemicals from discharged fire extinguishers. It remains unclear what role, if any, chemical irritants played in Sicknick’s death.

The U.S. Capitol Police issued a statement, Friday, stating that the medical examiner’s report into Sicknick’s death "is not yet complete" and they are "awaiting toxicology results."

The USCP statement on went on to say, "Sicknick’s family has asked for privacy during this difficult time and that the spreading of misinformation stop regarding the cause of his death."

Sicknick was "injured while physically engaging with protestors" on Jan. 6 and collapsed after returning to his division office, the Capitol Police said in a statement. He was taken to a local hospital for treatment and remained hospitalized until he succumbed to his injuries on the evening of Jan 7.

The suspect or suspects are being investigated for allegedly assaulting a federal officer or officers.

The union representing United States Capitol Police officers said on Sunday that "many" members of the force are looking to retire from or leave the federal law enforcement agency after the Jan. 6 insurrection.

"Many officers that are retirement eligible are seriously looking at turning in their retirement papers. Since January 6th, several Officers have retired as a result," Gus Papathanasiou, chairman of the United States Capitol Police Labor Committee, said in a statement Friday. "Additionally, I cannot tell you the number of younger officers who have confided in me since the insurrection who are actively looking at other police agencies or even new careers."

An ABC News investigation into the over 235 people federally charged for their alleged involvement in the Jan. 6 insurrection at the United States Capitol -- based on court records, interviews, and available news reports -- found that at least 20 individuals accused of storming the Capitol have since been charged with conspiracy.

Among the 20 charged with conspiracy, 10 individuals accused of being associated with, or interacting with, the Proud Boys and nine individuals are accused of being associated with, or interacting with, the Oath Keepers.

At least 34 individuals arrested are accused of being members of or associated with extremist groups, or of having interacted with them during the riot, according to court records, interviews, and available news report, including the Proud Boys, the Oath Keepers, or the Three Percenters.