Which one of the Gutter boys did it?

In the quest Wont Get Fooled Again, you are tasked with solving a murder most foul. I immediately noticed the quadruplets had different weapons and knew their equipment was going to be the key to identifying the killer. The clues pertaining to their equipment were:

• The victim died of a bullet wound. (Wasn't the guy with the rocket launcher)
• One of the Gutter boys ran into Moxxi's looking for a safe haven. He had a shield.

Since only one of the gutter boys had a shield, the choice seemed obvious. When I accused him, One of the other suspects yelled "WRONG" and ran away. I completed the quest and got the reward. Did I miss something here? Is this a scripted failure? Would I have gotten a better reward if I had chosen correctly?

Note: Dr. Zed said he "healed one up as good as new", but I didn't see any evidence of this on any of them.

You were almost there. The clues are:

• Bullet Wound (Marshal Friedman tells you)
• Guy had a shield (Moxxi tells you)
• Guy now has full health (Dr. Zed healed him)

If you back up so the accuse option goes away, you'll see their health/shields instead.

Because it was a bullet wound we know it's not the guy with the rocket launcher (far right). Because Moxxi said he had a shield we know it's not the guy on the far left (he doesn't have one).

This leaves the two guys in the middle, SMG guy and Sniper guy.

SMG guy is injured, not full health. Dr. Zed healed the guy so it wasn't him.

Only one left is sniper guy. He has a shield, full health, and a bullet weapon. Accuse sniper guy and he says "Yeah I did it, so what!?" and you've got him.

In order to complete this quest, you're going to need to do some investigating. Go and question Moxxi, Friedman and Zed to get information on what they think happened, listen to what they have to say and then return to the scene to accuse the killer.

"You would think that it’s the brother with the shield, but if you look at Justin’s hands, they form the type of weapon that was used; a sniper rifle from Barlo" - accuse him and complete the quest.

^Source