U.S. space scientist Stewart Nozette, who was sentenced March 21 to 13 years in prison for attempting to sell secrets to an undercover FBI agent posing as an Israeli spy, expressed regret as he spoke publicly for the first time since his arrest in 2009, The Washington Post reports.

Nozette said he accepted “full responsibility” for his actions and apologized to friends and family for any pain he had caused them. He also said he regretted not informing authorities when he was first approached about selling classified information.

During the sentencing hearing, federal prosecutors played a video in which Nozette, who had high-level security clearances during decades of government work on science and space projects at NASA and other agencies, is seen telling the FBI agent, “I gave you, in this first run, some of the most classified information that there is.” Later, after accepting an envelope stuffed with $10,000 in crash, he says, “I’ve crossed the Rubicon. I’ve made a career choice.”

As specified in a plea deal Nozette reached with prosecutors last year, he was sentenced to 13 years in prison and must pay $217,795 in restitution.