The union representing United States Capitol Police officers praised the "dedication and commitment" of those who protected the Capitol building one year ago.

"Today, we recognize the dedication and commitment to mission of the men and women who put their own lives and safety on the line to defend the U.S. Capitol," Gus Papathanasiou, chair of the union, said in a statement Thursday. "We especially pay tribute to Officer Sicknick who died after being injured during the rioting, and to Officer Liebengood who tragically took his own life after the attack."

According to Papathanasiou, 80 Capitol Police officers sustained injuries that day, with some so serious they are still not back at work. He said members of the force remain "committed to our mission," but that comes with an increase in officers as well as improved intelligence and communications between officers and leadership.

Papathanasiou noted that the legacy of Jan. 6 -- from a policing perspective -- should be a police force that is better prepared, with an eye toward readiness if an attack of such scale ever occurred again.

"Going forward, this Union will work with the Department to ensure those sacrifices will not be in vain," he added. "We must ensure that the events of January 6th are never repeated."

-ABC News' Luke Barr

On the evening of Jan. 5, 2021, on a sleepy street a short distance from the U.S. Capitol, a mysterious figure loomed. Wearing a sweatshirt with the hood pulled up, a pair of Air Max Speed Turf shoes with a yellow Nike logo, a backpack and gloves, the suspect walked through alleyways and was equipped with what investigators say were two pipe bombs.

A full year later, the agency still has not caught the person who placed the bombs nor has it released information about a "person of interest."

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-ABC News' Luke Barr

Beyond the riot, Jan. 6 was a dangerously close call. ABC News Chief Washington Correspondent Jonathan Karl asks: "What if Pence had followed Trump’s order? What would have happened if he had brought the gavel down during the joint session on Jan. 6 and thrown out Biden’s electoral votes in the states Trump had contested? What if he had declared Trump the winner of those states?"

J. Michael Luttig, a former federal appellate judge popular among conservatives, had advised Pence he would be violating the Constitution if he followed Trump’s order, and Luttig tells ABC News that if Pence had attempted to do it, he would have "plunged the country into a constitutional crisis of the highest order."

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-ABC News' chief Washington correspondent Jonathan Karl

As lawmakers returned the evening of Jan. 6 to certify the election following the attack, then-Vice President Mike Pence tweeted his thanks last year to the law enforcement officers who kept him safe, showing how he was rushed to a Capitol Hill parking garage during the attack.

In the subsequent weeks, video played at Trump’s second impeachment trial revealed just how close the rioters came -- some within 100 feet of Pence and his family, who were forced to take shelter in the Capitol.

In an interview with Trump for his book "Betrayal," ABC News Chief Washington Correspondent Jonathan Karl asked Trump at Mar-a-Lago last March if he was worried about the safety of his vice president.

"No, I thought he was well-protected," Trump said. "And I had heard that he was in good shape.”

When asked directly about the "’Hang Mike Pence’” chants on tape, Trump said, "Well, the people were very angry. Because it's -- it's common sense, Jon, it's common sense, that you're supposed to protect -- How can you, if you know a vote is fraudulent, right — how can you pass on a fraudulent vote to Congress?"

There is no evidence to support Trump’s claims that he won the election over Biden, despite dozens of failed court battles last year.