The couple had been returning to their central Florida home from a missionary trip to Ecuador, where he was handing out eyeglasses to the poor. Buechner works for the Council on Quality and Leadership, a nonprofit focused on improving life for people with disabilities and mental illness, the organization said in a statement.
She did not speak publicly Thursday. But in Costa Rica, Alpizar's brother told The Orlando Sentinel he didn't understand how marshals couldn't overpower an unarmed, single man that had cleared every security check.
"I will never accept that it was necessary to kill him as if he was some dangerous criminal," Carlos Alpizar said.
Associated Press writers Andrew Bridges, Mark Sherman and Lara Jakes Jordan in Washington; Mike Schneider and Travis Reed in Orlando; and Jessica Gresko and Tim Reynolds in Miami contributed to this story.