Is there any reason to think it was a Muslim? I didn't see it but I would assume it was the usual hateful lot seeing an opportunity to threaten her with violence (not that they need one)
The username was Meer Asif Aziz. Newspaper reports say Aziz is based in Karachi, though whether that is based on his Twitter bio or other info (eg his IP address) I don't know.
IF that is his real name, and IF he's based in Karachi, it sounds more like an angry Islamist than a TRA. And perhaps that's why the police are treating it more seriously than the thousands of other death threats she's received - they assume an angry Muslim making death threats is more likely to act on them than the usual whey-faced trans activist typing away in his mum's basement.
But you can't really tell, can you? What I mean is: you can't tell if that's his real name, you can't tell if he's based in Karachi, you can't tell if the death threat is genuine or just nastiness, you can't tell if he's a TRA or an Islamist or one of the many sad tossers who stalk Twitter or even some paid scrote in a Russian troll farm stirring up trouble.
On the internet, no one knows you're a dog.