A friend of mine came back from a nearby mountain with this flower from a wild shrub that was very common in the area where he walked. The area where these are found is the west-Alps, around -1300- 1500 meters above sea-level.
*After a while, I went back to take pictures myself and found flowers had turned into berries (some where already getting red) - see edit #2.
It is a very bee-attractive shrub, so he was considering planting some at his place where he raises bees.
Do you have any idea what this is? I'm sorry about the picture, which is of poor quality. I will try to add a better one if we go back to the area and see some more.
I used this site and it lead me to my first guess that it was some kind of cherry tree: http://www.forestry.gov.uk/forestry/infd-5mhe49
Simple - not lobed - linear - alternate - < 10 cm long - twigs shiny dark brown, and the leaf edged with small teeth / shiny dark brown twigssmall sharp teeth
... since its an UK site, mountain shrub are not there described ... still looking ...
So I went back to where my friend had spotted the thing, and found the bushes, scattered every now and then. Here is how it looks in the real (flowers are now gone unfortunately) - that's the thing in front of the pine tree: And here is the biggest we found - about 2-3 meters long.
Very similar cousin
It has a very similar cousin that grows in the very same location, but much bigger (maybe 4-5 meters), with white flowers, and that has some kind of white feather beneath the leaves:
The bigger cousin is here compared with my mysterious shrub; it's the one on the right - very similar indeed: