Making a play on a runner who reaches and passes first base...

[greymule]

In Fed, a runner who overruns (or overwalks) 1B on a walk is liable to be put out.

It's not as clear in OBR. The BRD quotes a MLB umpire as saying that the BR is liable to be put out unless there was some reason for him to run hard to 1B. I guess this might mean a pitch getting away from the catcher on ball 4 or something. Or maybe he thinks ball 4 was strike 3 uncaught and runs hard.

Don't have my book with me, so I'm not sure about NCAA. I think the BR can overrun safely on a walk.

Be sure you don't take "turns left" literally. After overrunning 1B, the BR can turn left without making himself liable to be put out, as long as he doesn't make some sort of aggressive move toward 2B.