The FBI said it is targeting a single assailant as it continues to investigate the death of U.S. Capitol police Officer Brian Sicknick, who died from injuries sustained in the Jan. 6 riot.
A federal law enforcement source and another close to the investigation confirmed the news on Saturday.
Sicknick, 42, was injured "while physically engaging with protesters" and returned to his division office, where he collapsed, according to a Capitol police statement. He was taken to the hospital, where he later died on Jan. 7.
Agents have not pinpointed Sicknick's exact cause of injuries, but recently said they suspect it was from a potential spray-type irritant, such as bear spray, that he inhaled during the riot. The investigation into Sicknick's death is being treated as an assault.
According to officials, a video shows a person attacking several officers, including Sicknick, with spray. The suspect is also heard discussing the alleged attack prior to the incident, officials said.
Federal authorities have not identified the suspect, and the FBI is not yet releasing the video to the public.
Five people, including Sicknick, died after a mob of supporters of then-President Donald Trump stormed the Capitol to stop Congress from formally accepting the Electoral College votes that delivered November's election to President Joe Biden.
Sicknick, who served in the New Jersey Air National Guard before joining the Capitol police in 2008, was honored this month by lawmakers after he had the rare distinction of lying in honor in the building's Rotunda.
His cremains were laid to rest at Arlington National Cemetery.
“Our promise to Brian's family is that we will never forget his sacrifice," House Speaker Nancy Pelosi, D-Calif., said in remarks during the ceremony. "Each day, when members enter the Capitol, this temple of democracy, we will remember his sacrifice and that [of] others that day, who fought so hard to protect the Capitol and the Congress."
Trump was impeached on an article charging him with "incitement of insurrection" over the Jan. 6 riot, but he was acquitted by the Senate.