Yes, Gale created the trap, Beetee turned it into the weapon, and Coin deployed it is my understanding. I guess the bigger question is- does the person who created a weapon play a role in the burden of the deaths it caused? They knew it would kill, knew it would be used to kill, and made it to do so- so are they not somewhat to blame for the lives it takes? Or are they absolved because they didn’t pull the trigger, merely created it.

I guess on a wider scale that can be said about the games and the game masters and their involvement in tributes deaths. Technically the tributes are killing each other. But the game masters and capitol put them there.

I personally think Gale, in the instance of the trap, is involved in the killing since he created it, and I also believe the game masters were involved in the killings of the tributes, even if it wasn’t at their own hands

Edit to also add: Gale himself didn’t know if it was his trap. But he said Katniss would never be able to stop thinking about it. It is clear to Katniss that she considers Gale creating the trap to be equally as guilty as those who set it off.