Alostor (in a past life)

You sat and didn't smile, all the people walked by and rejoiced. And you alone were sad.
Alastor came up to you and said:

Don't be upset, be happy in this life, so don't be sad.
He stood over you for a little while longer and then said:

By the way, I see you don't have any friends, but how about I be your friend?
and you nodded with a smile.
and he said:

• And you needed friends, well, fine.
  Let's go for a walk somewhere then?
  and you wanted to say that you are ready to go with him to the ends of the earth.

and you will find out what happens next.

while no one sees, he kills people,
works on the radio,
makes people smile.