* Alan Poindexter, 50, flew two space shuttle missions
* He was killed in watercraft crash in Pensacola, Florida
* Poindexter headed Naval Postgraduate School in California (Adds details from investigator)
By Irene Klotz
CAPE CANAVERAL, Fla., July 2 (Reuters) - Alan Poindexter, a two-time space shuttle astronaut, has died after a personal watercraft accident in Pensacola, Florida, NASA said on Monday.
Poindexter, 50, was riding WaveRunners with his two sons in Little Sabine Bay at Pensacola Beach on Sunday when the accident occurred, a spokesman for the Florida Fish and Wildlife Conservation Commission said.
Poindexter and his 22-year-old son Samuel were riding on one WaveRunner and his older son, 26-year-old Zachary, was on another, spokesman Stan Kirkland said.
"They stopped and apparently Zachary did not see them stop," Kirkland said. "He struck the right rear or the right stern of their personal watercraft. His watercraft went up and apparently struck Captain Poindexter in the back. Both Captain Poindexter and Samuel were ejected."
The former astronaut was pulled from the water and taken to the beach where friends attempted to revive him. He was flown by helicopter to Baptist Hospital where he died from his injuries, Kirkland said.
Poindexter's sons were not injured. All three men were wearing life jackets as required by law, Kirkland said.
"It's technically still under investigation until our report is completed," he said, but added that investigators were satisfied it was an accident and considered it "a terrible tragedy."
Poindexter is the son of former U.S. National Security Adviser John Poindexter, who served in the Reagan administration.
Poindexter, who went by the nickname "Dex," made two space flights during his career with NASA. In February 2008, he was the pilot aboard the shuttle Atlantis on a mission to deliver the European Space Agency's Columbus laboratory module to the International Space Station.
Poindexter returned to space in April 2010 as commander of the shuttle Discovery on one of the final cargo runs to the station before the shuttles were retired.
“"The NASA family was sad to learn of the passing of our former friend and colleague Alan Poindexter," NASA wrote in a Facebook post. “"Our thought and hearts are with his family."
“"He was a talented, courageous Navy veteran with gifts," astronaut Greg Johnson wrote on Twitter. "“Dex was a lovable guy with a strong work ethic."
A captain in the U.S. Navy, Poindexter left NASA in December 2010 to become dean of students at the Naval Postgraduate School in Monterey, California. He earned a master of science degree in aeronautical engineering from the school in 1995.
Poindexter was born in 1961 in Pasadena, California, but considered Rockville, Maryland, to be his hometown. He earned a bachelor of aerospace engineering degree from the Georgia Institute of Technology, then was commissioned in the Navy.
Poindexter flew combat missions in Iraq during Operation Desert Storm and Operation Southern Watch, then became a test pilot. He logged more than 4,000 hours flying time in more than 30 types of aircraft.
He was selected to join NASA's astronaut corps in June 1998. His wife Lisa is from Gulf Breeze, Florida, near where the accident occurred. (Additional reporting by Jane Sutton; Editing by Will Dunham)