President Obama interrupted the White House press briefing this afternoon to confirm that Justice David Souter called to share his decision to retire from the Supreme Court.
In a letter to the president, Souter wrote that he intends to retire when the court recesses in June.
Obama said he is "incredibly grateful" for Souter's "dedicated service," and praised him for having "shown what it means to be a fair-minded and independent judge."
Souter's announcement apparently did not catch the president off guard, as administration sources told ABC News today that officials have been preparing for a Supreme Court vacancy since just a few weeks after the election.
A group of officials began work shortly after Obama's victory to identify candidates for vacancies in the appellate court as well as the highest court in the land, anticipating that there would be a vacancy in the Supreme Court this term.
Souter, Obama said, "consistently defied labels and rejected absolutes, focusing instead on just one task: reaching a just result in the case that was before him."
As for selecting Souter's replacement, Obama said it "is among my most serious responsibilities as president," and that he intends to consult with both Republicans and Democrats during the process.
"I will seek somebody with a sharp and independent mind and a record of excellence and integrity," Obama told the gathered reporters. "I will seek someone who understands that justice isn't about some abstract legal theory or footnote in a case book, it is also about how our laws affect the daily realities of people's lives."
Obama said he views the quality of empathy, "of understanding and identifying with people's hopes and struggles, as an essential ingredient for arriving at just decisions and outcomes."
"I will seek somebody who is dedicated to the rule of law. Who honors our constitutional traditions. Who respects the integrity of the judicial process and the appropriate limits of the judicial role," Obama said.
Souter's decision to retire comes as a surprise to many, including some of his colleagues on the court. At least one justice learned of it from media reports.
At 69 years old, Souter's younger than five of his fellow justices, and 20 years younger than the oldest justice, John Paul Stevens. For the highest court in the United States, Souter's just hitting his prime.
Still, the clues have been there. Speculation started to swirl this spring because Souter, who usually waits to hire clerks during the summer, hadn't even started interviewing clerks for the next term.
He also famously hated the Washington, D.C. lifestyle, joking that his work on the court was a "sort of annual intellectual lobotomy." He much preferred his native New Hampshire, where he could sit by the fire in his drafty cabin and read his beloved books.
"He has a very strong sense of what he likes to spend his time doing, and hobnobbing isn't high on the list," said Meir Feder, one of Souter's clerks from the 1990 term.
Obama's Chance to Shape the Supreme Court
Souter's retirement will give President Obama, himself a former law professor, his first chance to shape the court. Though it won't change the direction of the court, it gives Obama the chance to secure the seat for liberals for a generation.
"It definitely is a test for the Obama administration, for the president," ABC News' George Stephanopoulos told "Good Morning America". "It will reveal a lot about his feelings, his ideology, where he wants to take the court, where he wants to take the country."
Obama's comments today echo what he said during his campaign, when he vowed to appoint a judge who would fight for those who couldn't fight for themselves.
"We need somebody who's got the heart -- the empathy -- to recognize what it's like to be a young teenage mom. The empathy to understand what it's like to be poor or African-American or gay or disabled or old. And that's the criteria by which I'll be selecting my judges," he said in July 2007.
And in March 2008, Obama again explained what he believes makes a reasonable judge.
"Some of our best justices have been people who knew a little bit about how the world works. ... I want my judges to understand that part of the role of the court is to look out for the people who don't have political power, the people who are on the outside, the people who aren't represented, the people who don't have a lot of money," Obama said.
Obama added to his March 2008 remarks that he "absolutely" wants women on the court, and it's widely expected he will use this opportunity to appoint another woman to the bench. Out of nine Justices, Ruth Bader Ginsburg is the only woman currently serving on the court.
Stephanopoulos said the leading candidate could be Sonia Sotomayor, a federal appeals judge. If nominated and confirmed, she would be the first Hispanic to join the court.
Stephanopoulos said Sotomayor's story is one of the American dream, as she worked her way up from housing projects in the Bronx to Princeton and Yale Law School. And a Republican -- George H.W. Bush -- first nominated her to the bench.
The list of possible contenders could also include Elena Kagan, Diane Wood or Leah Ward Sears.
Kagan is the former dean of Harvard Law School who Obama picked to serve as solicitor general, the U.S. government's litigator before the Supreme Court. Wood serves as a federal appeals judge in Chicago, and Sears, the first African-American woman to serve as a Superior Court Judge in Georgia, is the chief justice on that state's Supreme Court.
The opportunity to choose at least one Supreme Court justice is expected during most presidencies, and rumors of retirements seem to spike near the end of each term as other concerns surface.
Adding to Obama's Already Packed Agenda
Speculation ramped up about a possible Ginsburg retirement, as she is battling cancer for the second time. But even though she underwent surgery for pancreatic cancer during a recess in February, Ginsburg hasn't missed a day of work on the court and has stated that she plans to stay on for the near future.
Replacing a member of the court will round out Obama's already packed agenda, loaded with initiatives concerning the economy, health care, energy and foreign policy.
"They have been thinking about this already, you would expect them to want to have someone in place before the court's next term begins in October," Stephanopoulos said. Obama said today that he hopes to have the next Justice sworn for that fall term.
The Supreme Court is scheduled to complete its current term in June. Nomination and confirmation hearings could go on during the summer in preparation for the court reconvening in October.
Stephanopoulos said the selection process for a Supreme Court nominee will likely be headed by White House counsel Greg Craig, but that Vice President Joe Biden, who served on the Senate Judiciary Committee during six Supreme Court confirmations, could also play a big role.
President George H.W. Bush appointed Souter to the court in 1990. Souter came out of nowhere, a blank slate, unknown outside his home state of New Hampshire.
Bush had been assured that the quiet New Englander would be a solid conservative.
"If it were possible for me to express to you the realization that I have of the honor which the president has just done me, I would try, and I would keep you here as long tonight as I had to do to get it out," Souter said of his nomination.
But Souter was a surprise, and to conservatives, a mistake. He became one of the court's most reliable liberals.
"Justice Souter was somebody who came into every case with an open mind," said Feder, his former clerk.
Feder recalled several of Souter's most memorable opinions that defined his place on the court.
Souter's Legacy: Memorable Decisions
"What will be most remembered," Feder told ABC News, is his role in the 1992 decision that reaffirmed Roe v. Wade.
"At the time, most people expected that the recent appointments to the court would result in Roe being gutted or overruled. He wrote the part of the opinion stressing how important it was for court to respect prior decisions and not let major constitutional principles swing back and forth with every new appointment," Feder said. "Aside from the obvious importance of the opinion, it captures a fundamental part of his approach to judging."
Noting that Souter is a "deeply religious person himself," Feder said he "regularly voted to keep government out of religious matters" such as school prayer or the creation of a special school district for a religious sect.
"And Bush v. Gore has to be mentioned," Feder added. "He dissented from the decision to stop the Florida recount, and it's widely understood that he was deeply disillusioned by what the court did there."
An eccentric bachelor with a spartan lifestyle, Souter disliked Washington and for years has told friends he longed to go home. And now it appears he will get his wish.
ABC News Senior White House Correspondent Jake Tapper contributed to this report.