Why did David Toms withdraw from todays round at the U.S. Open Golf Championship.?

Question

In todays 2nd round of the U.S. Open Golf Championship, David Toms withdrew from competition and did not play his second round. I would like to know why?

Answer 1

injury

Answer 2

He injured his back on the 12th hole during Thursday's round and about 2 hours before he was scheduled to start his second round he decided to withdraw. He was able to finish his first round in 79 dispite his injury. He pared the par 5 12th and was +7 up until that point, and he finished the remaining 6 holes 2 over par.