At the very least, I'd like to see the GOP leaders in Congress call a news conference, and one by one take the mic and say, "I'm sorry."

It's kinda the least they could do.  

It's not like anyone doesn't understand, pro or con guns, that the GOP leadership is responsible for it being possible for the Texas shooter, the Las Vegas Shooter, etc. to get ahold of the guns they used to kill scores of people.

At the very least, they could apologize for the cynical political position they've taken, which has led to those results.

People died because the GOP panders to the NRA-ish gun lobby.   Their votes, or refusal to vote, in order to make meaningful changes to American gun law is a direct reason, cause, and result of mass gun deaths in the US.

There's just no getting around that.  Make those guns illegal and eradicate them, and they are not available for mass murder.