(Reuters) - Retired U.S. astronaut Mark Kelly, married to former Congresswoman Gabby Giffords, who was wounded in a 2011 mass shooting, said on Tuesday he was challenging Republican Martha McSally for John McCain’s former U.S. Senate seat.

Giffords stepped down from Congress after sustaining a serious head injury in the attack but has emerged as one of the leading voices of the U.S. gun-control movement.

In a 4-1/2 minute video, Kelly sits on a sofa next to Giffords discussing his mother’s history as a police officer as well as the attack on his wife.

“I thought that I had the risky job. It turned out that you were the one who had the risky job,” said Kelly, a former U.S. Navy combat pilot and space shuttle commander.

McSally, a former U.S. Air Force combat pilot, was appointed last year to the seat held by the late McCain. A special election will be held in 2020 to determine who will serve the last two years of the term.

McSally narrowly lost a campaign for the state’s other Senate seat to Democrat Kyrsten Sinema in November. Sinema won the seat formerly held by Republican Jeff Flake, a vocal critic of President Donald Trump who did not seek re-election.

Kelly said problems he wanted to take on include climate change, the rising cost of healthcare and increasing economic inequality.

“We’ve seen this retreat from science and data and facts and if we don’t take these issues seriously, we can’t solve these problems,” he said in the video.