Where was Lebanon's army when Beirut was being bombed by the Zionists?

Why are Lebanese soldiers fighting so ferociously against their Arab brothers? Why are they pounding a Palestinian refugee camp so hard with artillery and tank guns and killing civilians?
 
It's really hard to understand what is happening in Lebanon.

Why are Lebanese soldiers fighting so ferociously against their Arab brothers? Why are they pounding a Palestinian refugee camp so hard with artillery and tank guns and killing civilians?

Where were they last summer when their country was being invaded by the Zionists? Where were they when Beirut was being bombarded by Zionist planes and missiles... when their own brothers and sisters were being murdered?

Can anyone call these army soldiers heroic defenders of their country? Shouldn't they show this bravery towards foreign invaders and occupiers and try to rescue their brothers and sisters who are languishing in Zionist jails?

Instead of attacking displaced Palestinians, they should show more compassion, love and understanding towards their own brothers living in terrible conditions in refugee camps. They should be brave and fight their enemy, not their brothers!