BBM
By the end of the day of the murders, police had announced to the public that the suspect was born in Cardiff, and attempted to get on top of all the lies being told by a certain segment of social media (he was not a refugee, nor a migrant who came on a boat, not on a special watch list, etc, etc, etc). They said from nearly the very beginning they did not believe it was a terrorist attack.
What is allegedly being kept secret? It's fairly standard for law enforcement to ask for random speculation to stop since it can be detrimental to ongoing investigations. They've done the exact same thing in several high profile cases, like Nicola Bulley.
All of these riots have nothing to do with this tragic situation. It's an excuse for people to exercise their racist and xenophobic views, because the suspect is a brown guy. Even though he was born in Cardiff, he is "other".
MOO