Hypothetical

What if, when Brooks goes to confront Eric in the parking lot moments before the massacre he insists on seeing what's inside Eric's duffel bag and even makes an attempt to go open it. Does Eric out of necessity shoot him right there or...... your thoughts.

I don't think he'd risk shooting Brooks. But he probably would be quick on his feet saying it was video equipment and not to touch his shit if Brooks tried to grab the bag. He may have just let Brooks go into the school if he persisted.

I don't think Eric would have shot him. He probably would have just made up an excuse, and Brooks didn't really have reason to believe anything sinister was in the bag so he may have just dropped the whole thing.

I think the only scenario where Eric shoots Brooks would be if he found out and tried to alert others of what they were about to do.

I think Eric would have told Brooks to "F*ck off" if he had insisted on seeing what was in his bags.

But as Littlelo said, Brooks had no reason to suspect that Eric had anything dangerous in them, so he wouldn't have demanded to see the contents. I also think that Brooks wouldn't have been very pushy because he knew how Eric's temper could be.

Brook probably wouldn't have asked to see what's inside the bag. As he said, it didn't seem like anything was out of the ordinary.
If he did, Eric would have probably just told him to go away and not touch the bag.
He wouldn't have even had the chance to shoot him, considering he didn't have his weapons on him when he arrived. They were in his trunk inside several different backpacks.