It appears that the surgeon and “journalist” are both utterly ignorant on the subject of small-arms ammunition, and have an anti-RKBA bias.
“Dum-Dum” was the name of a manufacturing plant in India around a hundred years ago.
Their bullets were not really unusual, they just featured an exposed lead tip, now legally required for hunting in most states.
Most “Self Defense” ammunition has either an exposed lead tip, or a hollow cavity in the nose.
By this articles standard nearly all non-FMJ (Full Metal Jacket) ammunition is “Dum-Dum” type, in reality the “Dum-Dum” moniker has become a pejorative term favored by gun banners.
In my collection I have some of the “Anti-Terrorism” ammunition Israel developed after the Munich massacre, it is a hollow cylinder of brass, with a plastic plug to enable reliable feeding.
It leaves a hollow wound track to drain the body of blood, and a core of detached tissue that will NOT heal.
We can be glad this nut did not use that sort of ammunition.
We may be glad he did not use any of several types of expanding ammunition either, not being a doctor I am not certain which bullet type is more lethal (something even the experts debate endlessly), but the frangible bullets were less likely to pass through one victim and strike a second.
From the description is appears he used frangible ammunition, composed of a compressed and molded metallic powder.
This is actually a “Safety” ammunition, designed to prevent ricochet or over-penetration of building walls.
It is commonly used by cops, air marshals, and security guards.
It is designed to dump it’s energy in the target without exiting so as to protect bystanders, it will not typically puncture an airplane fuselage.
Stating that the nutso shooter used “Safety” ammunition would not serve the agenda of the authors, so they trotted out the Dum-Dum fiction instead.