Rep. Gabrielle Giffords married astronaut Mark Kelly in 2007. Kelly is scheduled to fly the shuttle in three months. COURTESY OF REP. GIFFORDS'OFFICE

CAPE CANAVERAL, Fla. - The shocking gun-down of Rep. Gabrielle Giffords has left NASA reeling: Her astronaut husband was due to rocket away in just three months as perhaps the last space shuttle commander, and her brother-in-law is now aboard the International Space Station.

Shuttle commander Mark Kelly rushed to his wife's hospital bedside Saturday as his identical twin, Scott, did his best to keep updated on the shooting through Mission Control, the Internet and the lone phone aboard the space station.

"I want to thank everyone for their thoughts and prayers, words of condolences and encouragement for the victims and their families of this horrific event," Scott Kelly tweeted from space.

"What is going on in our country that such a good person can be the subject of such senseless violence?"

It was the worst news to befall an astronaut in orbit since Christmas 2007, when a space station resident learned of his mother's death in a car-train collision.

NASA officials said it was premature to speculate on whether Mark Kelly would step down as commander of the April flight of the shuttle Endeavour.

But it was hard to imagine how he could keep up with the grueling training in the next three months, primarily in Houston, and still spend time with his hospitalized wife.

Kelly's mission is higher in profile than most. Endeavour's final flight will deliver an elaborate physics experiment by a Nobel Prize winner. For now, anyway, it's slated to be the last voyage of the 30-year shuttle program.

That fact alone propelled 46-year-old Mark Kelly onto the cover of this month's Air & Space magazine of the Smithsonian Institution; he shares the cover with the first shuttle commander, moonwalker John Young.

In an interview with The Associated Press last fall, Kelly, a Navy officer and three-time shuttle flier, said it was "timing and luck" that snared him one last coveted commander's seat, not his influential wife. She loved sharing his adventure. "She's excited about going to Florida for the launch," he said then.

As for the rippling effects of Saturday's shooting, there is no precedent for anything like this at NASA. Astronauts have had to bow out of space missions over the decades, but never a commander so close to flight and never for something so brutal.

Mark Kelly's co-pilot, retired Air Force Col. Gregory Johnson, could take over. Or NASA could free up another astronaut.

"It is premature to speculate on any of this," NASA spokesman James Hartsfield said in an e-mail. "For now, the focus is on supporting Mark and Scott, and things need to be taken day by day, and all thoughts are with the victims."

NASA Administrator Charles Bolden called Giffords a "a long-term supporter of NASA . . . who not only has made lasting contributions to our country but is a strong advocate for the nation's space program and a member of the NASA family."

Mark Kelly's two teenage daughters from a previous marriage were reportedly with him in Tucson.

The couple met in China in 2003 during a young leaders' forum and married in November 2007 at an organic farm south of Tucson. Giffords served on the House Science and Technology Committee and took on NASA affairs while heading the space subcommittee.

She admitted to being nervous at her husband's shuttle launch in 2008. "It's a risky job," she told The Associated Press. "You don't really relax" until touchdown.

Mark Kelly readily accepted his wife's fame. He considered her the bigger star in the family.