According to the South Korean army, yes they shot at some water. For all you know that means they missed their target. The record is clear. Live fire was begun by the South Koreans.
Cueball come on man, I know you're smarter than this.
The South Koreans were doing a scheduled training drill the North Koreans knew about (but didn't like and demanded SK to cancel) It involved practice artillery gunnery where SK artillery units were firing in the opposite direction from North Korea out to sea. You're assertion that the SK units fired on NK and missed their targets (thus starting the engagement) is pretty, I don't know, crazy and I hope it's from your lack of knowledge about how artillery units train and other things military. Please understand I'm not poking fun at you or anybody else here for not understanding this.
Where do you source this assertion that SK units were firing out to sea? Based on your knowledge of military practice? The fact that you don't have to aim at anything in order to practice gunnery, does not mean that they were not firing in the direction of NK.
Regardless, I highly doubt that standing orders for the North Korean army were to stand down until hit. I suspect that it would be much simpler than that. Fire if they start firing. Not "fire if anything lands on you".
You are being a tad bit gullible if you actually think that South Korea did not intend to get a live fire response, after they have been warned not to be there at all. Moreso, if you actually think that the US response agreeing to join military excersizes with a US fleet carriers is an idea that suddenly got tabled yesterday as an emergency measure.
You actually think the South Korean army commanders are so stupid as to believe that North Korea was not going to engage when South Korea started firing live round?