The IDF soldiers were on the "Israeli" side of the fence. When they crossed over the fence onto the "other side" then the Lebanese soldiers fired into the air i.e. they fired warning shots. REGARDLESS of wether or not the Lebanese were entitled to fire those warning shots (the "where is the border" argument) the IDF responded by firing missiles and tank shells **at** the Lebanese soldiers, at which point the Lebanese soldiers responded with sniper fire and RPGs. That appears to be the sequence of events, but we will know for sure when those UNIFIL observers in Adaisseh write their reports.....
Saudi king to meet with Obama on Friday amid Gulf concerns over Iran deal (Reuters)
from the article: 3 Lebanese soldiers, journalist killed in clash on Israel-Lebanon border