stealing second base

Question
r1 on 1st base. batter has a count of 1or2 strikes and 3 balls.  pitcher is in his set position. when pitcher begins delivery r1 takes off for 2nd in a steal attempt.  The catcher upon receiving pitch immediately throws to 2nd baseman who tags r1 before reaching 2nd base.  (R1 is sliding into 2nd base).  field umpire calls r1 out at second.  Plate umpire calls ball four and awards b1 1st base w/o liability and declares r1 safe at second because of walk on balls advances all runners.

is this correct?  If r1 attempted to steal 2nd base before there was a ball 4 is he allowed to advance on the walk w/o liability to be out?

What is the ruling on this?

thanks for your help.  everyone is divided on this issue.

Answer
That was the correct ruling.  If a batter is walked, all runners forced to move up on the walk by the batter taking first base are free to advance without play to the next base retroactive to the time of pitch.  In other words, as long as you weren't out when the pitcher let go of the ball, you get to advance without play to the next base and any plays made on a runner forced to advance are ignored.  One thing to keep in mind here, on a walk, no runner, INCLUDING the batter going to first base, may overrun his base.  If they do, they can be tagged out by a fielder in possesion of the ball.  I hope this answers your question.