Fear for welfare

What constitutes a fear for welfare incident? A sad situation near where I live where a police car was following a car because of fear for welfare. The car being followed hit a couple of cyclists and killed them.
But would speeding or dangerous / reckless driving constitute fear for welfare? Or suicidal thoughts? Or a passengers welfare?

Just curious, certainly don't think the police did anything remotely wrong from what I know. Seems odd yet specific wording.

[Red Herring]

A concern call is generally based on information suggesting someone is at risk of self harm, although it can be that they pose a threat to another. I'm sure it will come out eventually.

thanks, yes, I'm sure we'll find out in good time.

[daveyrach]

Even closer to where I am, happened in Purley not 5 mins from my house.

It made the South news. They seemed to think that police were trailing the car because they believed it to have been stolen.

Just spotted this on BBC News website http://www.bbc.co.uk/news/uk-england-berkshire-26208889

There are various historical cases of someone of the same name and age, looks like he's a career criminal with a difficult background. Can't imagine what the families of the victim are going through.

I had imagined that there was the welfare call when he was at a house or other location and then when he realised the police were coming, thats when he got into the car. Who knows though