Mass shootings maybe, but mass killings are usually white. Will research a list later. Neither Oklahoma nor 9/11 were black to start.
Depends on what you mean by "mass." They're nailing 3 here, 3 there, 5 here, 4 there, 3 here, 2 there. Pretty sure Timothy McVeigh has already been surpassed.
The reason is:
White people hold the pistol with the sights in the vertical position. In that way it is accurate.
Black people hold the pistol sideways with the sights to the side of the gun. In that way it is inaccurate.
The first method is good for you actually hit the target where you aim. The second method is terrible at accuracy and simply spews bullets everywhere. That is the difference between killing and maiming.