Three days after Capitol Police Officer Brian Sicknick died defending the Capitol against insurrectionists the White House lowered the U.S. flag to half-staff.

The decision to lower the flags came hours after Capitol Police also announced the off-duty death of Officer Howard Liebengood. The circumstances of his death have not been made public.

The U.S. attorney's office in Washington opened a federal murder investigation into the death of Sicknick, who died Thursday night after suffering injuries in the violent siege on Capitol Hill, three law enforcement sources confirmed to ABC News.

The investigation is being conducted jointly between the FBI and the D.C. Metropolitan Police Department, with cooperation from U.S. Capitol Police.
Acting Attorney General Jeffrey Rosen said in a statement that the Department of Justice "will spare no resources in investigating and holding accountable those responsible."

-ABC News' Elizabeth Thomas

Rep. David Cicilline, D-R.I., said on Twitter that an article of impeachment has just passed 200 cosponsors.

House Democrats were circulating the draft, citing "incitement of insurrection" on Friday and said they could introduce it as early as Monday and hold a vote as early as the middle of the week.

On Saturday, House Speaker Nancy Pelosi, in a letter to Democrats, asked members to prepare to return to Washington this week -- another signal that the House could take up and pass the impeachment article to the Senate after it is formally introduced.

The article charges Trump with "willfully inciting violence against the government of the United States" with his comments at the rally outside the White House that it says "encouraged—and foreseeably resulted in—imminent lawless action at the Capitol."

-ABC News' Benjamin Siegel

While Many Democrats have renewed calls to impeach Trump, following his supporters' storming of the U.S. Capitol on Wednesday, Illinois Republican Rep. Adam Kinzinger said on ABC's "This Week" that he doesn't think impeachment is "the smart move" right now.

He did, however, call for the president to resign or be removed by the 25th Amendment.

"I think it victimizes Donald Trump again and I think there's a moment that we're in right now where Donald Trump, he's looking really, really bad," Kinzinger told ABC News Chief Anchor George Stephanopoulos.

"I'll vote the right way, you know, if I'm presented with that, I just think it's probably not the smartest move right now but I think that's going to be out of my hands," he added.

Rep. Alexandria Ocasio-Cortez, D-N.Y. said she believes that a second impeachment of President Donald Trump should be scheduled.

"Our main priority is to ensure the removal of Donald Trump as president of the United States," Ocasio-Cortez told ABC News Chief Anchor George Stephanopoulos on Sunday. "Every minute and every hour that he is in office represents a clear and present danger, not just to the United States Congress but frankly to the country."

"We're also talking about complete barring of the president -- or rather of Donald Trump -- from running for office ever again," she added. "And in addition to that the potential ability to prevent pardoning himself from those charges that he was impeached for."

Trump 'represents a clear and present danger' to Congress, country: Ocasio-Cortez

Election Day is here in the two runoff races in Georgia that will determine whether Democrats or Republicans control the Senate, but there is unlikely to be a result Tuesday night, and it could be days until there is a clear winner.

There's a strong chance that there will be a "red mirage" -- the early but misleading appearance that Republicans have won -- similar to what was seen in the general election in several battleground states.

Trump was leading by tens of thousands of votes in Georgia on election night in November, a fact not unique to the state but something President Trump and his allies cite when claiming baselessly that the election was rigged against him. 

It wasn't until Clayton County, the fifth largest and the most Democratic in the state, uploaded a batch of votes in the early hours of the Friday after the election that Biden surpassed Trump and took the lead in Georgia. 

In the Senate races, the six largest counties -- which all lean in Democrats' favor -- are going to take longer to count their votes than small, rural counties, which lean in Republicans' favor. 

Also, absentee ballots can be received up until 7 p.m. on Election Day, and these will still need to be processed, which is time-consuming. Voters whose absentee ballots are rejected (like for a missing signature) have until 5 p.m. Friday to "cure" their ballots. Military/overseas ballots are due by 5 p.m. on Friday as well. Voters who had to cast provisional ballots because they didn't have a photo ID also must follow up with their county election offices and prove their eligibility to vote by 5 p.m. Friday. 

On election night and in the days that follow, a "red mirage" or "blue shift" is not a sign that something nefarious is happening -- it just means the votes are being counted.

-ABC News' Quinn Scanlan