If he was using a bullet of .308 diameter or smaller, he should have been using varmint bullets. These are widely used on small, thin-skinned animals like prairie dogs, ground squirrels, coyotes, foxes, etc. They often have very thin copper jackets, sintered lead cores, and a plastic tip to start violent expansion upon impact. They dump most all of their energy in the first two to three inches of tissue to prevent over-penetration and downrange hazards.
If anyone wants to see an example, google “Hornady V-max”. I have no information as to his choice of ammunition, bullet or even what caliber he used. Varmint bullets simply match the description of the wound ballistics given by the doctors quoted in the articles.
“Dum-dum” bullets are such arcane nonsense that only people as ignorant of firearms as the British would use it. Using terms like “dum-dum” and “cordite” is part of why nothing written by the British media about firearms is accurate or trustworthy.
Remember when Reagan was shot? ‘Exploding .22lr bullets’. The reporters in Euroweenieland are probably having to dig into shooting reports from famous cases, to get a ‘working knowledge’ of bullets and weapons. Media whoredom is not so bright anymore.