Sen. Patrick Leahy was officially sworn in as the third-in-line for the presidency, following the death of Sen. Inouye. 

Connecticut Sens. Joe Lieberman (I) and Richard Blumenthal (D) mourned the victims of the “senseless, horrific attack” on the Senate floor Tuesday.

A mass shooting took place last Friday at Sandy Hook Elementary School in Newtown, Conn., killing 20 children and six adults. The two senators said, “these dead should not have died in vain,” while calling for gun-control reform to prevent future killings.

“I don’t blame people for being skeptical, we should have acted earlier,” Lieberman said Tuesday. “But that doesn’t mean we shouldn’t hear the cries of those children as that mad man turned on them.”

House Democrats returned to the floor Tuesday morning to keep up their call for new gun-control legislation, and they had several specific proposals in mind in reaction to last week's shooting deaths of 26 people, including 20 children, in Newtown, Conn.

Reps. Earl Blumenauer (D-Ore.) and Mike Quigley (D-Ill.) called for a renewal of the assault weapon ban that expired in 2004, a ban on guns with high-capacity magazines, and tougher rules for buying guns at gun shows without documentation.

Senate leaders marked Sen. Daniel Inouye’s (D-Hawaii) death by having a moment of silence in the Senate Tuesday.

Inouye died Monday afternoon at the age of 88. He had been hospitalized earlier this month at the Walter Reed National Military Medical Center in Bethesda, Md., for respiratory complications.

The House and Senate passed identical resolutions on Monday that mourn the loss of the 26 killed in last week's shooting in Newtown, Conn., and say both chambers are "committed to working together to help prevent tragedies like this from ever happening again."

The resolutions — H.Res. 833 and S. 621 — do not make a specific pledge to strengthen gun control laws. But the resolutions were passed on the same day that several Democrats resumed their calls for tougher laws, particularly those that would ban guns that can fire dozens of rounds per minute.

The House meets at 10 a.m. for speeches, then at noon for work on up to seven suspension bills, including one aimed at thwarting Iran's policy goals in the Western Hemisphere.

Votes on some or all of these bills are expected to start at the end of the day.

Rep. Jim Himes (D-Conn.) said Monday that he would motivate himself to push for stricter gun control laws by imagining that two of the young victims of last week's shooting in Newtown, Connecticut would ask him to pass these bills if they were alive.

"I tell you how I'm going to challenge myself," Himes said on the House floor. "I'm going to imagine Noah and Jack, six-year olds who nobody really knew, I didn't know them… I'm going to imagine them standing right here — and that's not hard for me with a ten year old and a 13-year old at home — looking up and asking, will you do it?"

The Senate passed a resolution Monday evening recognizing Sen. Patrick Leahy (D-Vt.) as the third in line for the presidency as president pro-temp of the Senate.

The resolution, S. Res. 619, came just hours after Sen. Daniel Inouye (D-Hawaii) — the former pro-temp — died.

As the Senate ended business for the day, it passed a several other measures by unanimous consent Monday.

The House passed two bills dealing with federal land use in two roll call votes, and then was set to hear speeches from members, likely on the Newtown, Connecticut shooting on Friday, and possibly on today's news that Sen. Daniel Inouye (D-Hawaii) died.

In between the votes, the House held a moment of silence for the victims of last Friday's shootings in Connecticut, which was preceded by remarks from Rep. Chris Murray (D-Conn.).