U.S. officials have arrested and charged two men with assaulting U.S. Capitol Police officer Brian Sicknick with bear spray during the Jan. 6 riot, but they do not know yet whether it caused the officer’s death.

George Tanios, 39, of Morgantown, West Virginia, and Julian Khater, 32, of Pennsylvania, were arrested Sunday on an array of charges, including assaulting a federal officer with a dangerous weapon, conspiracy and other offenses. The idea that Sicknick died after being sprayed by a chemical irritant has emerged in recent weeks as a new theory in the case.

The arrests are the closest federal prosecutors have come to identifying and charging anyone associated with the deaths that happened during and after the riot. Five people died, including a woman who was shot by a police officer inside the Capitol. But many rioters are facing charges of injuring police officers, who were attacked with bats, sprayed with irritants, punched and kicked, and rammed with metal gates meant to keep the insurrectionists from the Capitol.

Investigators initially believed that Sicknick was hit in the head with a fire extinguisher, based on statements collected early in the investigation, according to two people familiar with the case. But as they’ve collected more evidence, the theory of the case has evolved and investigators now believe Sicknick may have ingested a chemical substance — possibly bear spray — that may have contributed to his death, officials have said.

Sicknick and other officers were standing guard behind metal bicycle racks as the mob descended on the Capitol on Jan. 6.

“Give me that bear shit,” Khater said before he reached into Tanios’ backpack, according to court papers. Tanios told Khater “not yet” because it was “still early,” but Khater responded that “they just f—ing sprayed me.” Khater was then seen holding a can of chemical spray, prosecutors say.

Khater walked through the crowd toward the bike rack barrier. Rioters began pulling on one of the racks, and Khater was seen with his arm in the air and the canister in his hand while standing just 5-to-8 feet from the officers, authorities said.

Video footage shows the officers reacting one by one — bringing their hands to their face and rushing to find water to flush out their eyes — after they were hit with the spray, according to court papers.

Another officer eventually spotted Khater deploying the substance and sprayed Khater himself, authorities said.

The men each made brief court appearances from jail via videoconference on Monday and will remain locked up pending future hearings. A detention hearing was scheduled for Thursday for Tanios.

An email seeking comment was sent to Tanios’ lawyer. A person who answered the phone at the office of Khater’s lawyer said they had no comment.

In a statement Monday, Capitol Police Acting Chief Yogananda Pittman called the attack on the Capitol and its officers “an attack on our democracy.”

“Those who perpetrated these heinous crimes must be held accountable, and — let me be clear — these unlawful actions are not and will not be tolerated by this Department,” Pittman said.

The FBI had obtained video of the incident and released photos of both of the men, but did not indicate in wanted posters that they were being sought in connection with Sicknick’s death. A former colleague identified Khater and the FBI received a tip from Tanios’ former business partner, who also alleged he embezzled hundreds of thousands of dollars from their business, court papers said.

Tanios operates a greasy spoon called Sandwich U in Morgantown, home of West Virginia University.

On social media, he has referred to himself as the “Sandwich Nazi” and has tangled with customers and former employees in online comments. In 2019 on Instagram, he gleefully promoted a one-star Google review that said, “If donald trump was a restaurant manager, this is who he would be.”

A photo at the Capitol cited in his charging document shows him wearing a sweatshirt with the logo of his restaurant.

Sicknick died after defending the Capitol against the mob that stormed the building as Congress was voting to certify Joe Biden’s electoral win over Donald Trump. It came after Trump urged supporters on the National Mall to “fight like hell” to overturn his defeat.

The circumstances surrounding Sicknick’s death remain unclear, and a final cause of death has not been determined. Capitol Police have said he died after he was injured “while physically engaging with protesters” and the agency’s acting chief said officials consider it a line-of-duty death.

Sicknick collapsed later on and died at a hospital on Jan. 7. The Justice Department opened a federal murder investigation into his death, but prosecutors are still evaluating what other specific charges could be brought in the case and the probe continues, officials have said.

The medical examiner’s report on Sicknick’s death is incomplete and no cause of death has been made public. Capitol Police say they are awaiting toxicology results.

The FBI has already released about 250 photos of people being sought for assaulting federal law enforcement officers during the riot. Some have already been arrested, and the Justice Department said about 300 people have been charged with federal offenses related to the riot.