The Senate begins its investigation of the Jan. 6 Capitol riot on Tuesday with a hearing that will feature testimony from four of the top security officials in charge that day. Three of them resigned soon after the attack amid criticism—former Senate Sergeant-at-Arms Michael Stenger, former House Sergeant-at-Arms Paul Irving, and former Capitol Police Chief Steven Sund, reports the New York Times. Robert Contee, chief of the Metropolitan Police Department, also will testify. Among the broad questions: Why did it take so long for support to be summoned? What was known of advance plans for the protest? What role did former President Trump play? But Politico notes that another question is expected to be addressed: What happened to Capitol Police officer Brian Sicknick?
Sicknick died "while physically engaging" rioters, according to the Capitol Police, but the circumstances remain murky. Initial reports that he was struck by a fire extinguisher have since been challenged, notes Politifact. Other reports suggested some kind of chemical irritant played a role or that Sicknick suffered a stroke. However, the officer's death remains under investigation, and authorities have not released details. It's possible that could change Tuesday, which will be the first time Stenger and Irving have spoken publicly about the riot and the security response. Meanwhile, the Washington Post warns in its preview that the joint hearing before two Senate committees could become a "battleground for competing narratives over what prompted the riot and who was responsible for it." (Read more Capitol attack stories.)