From your post a month ago I gathered that you're foremost interested in the loss of Lancaster ND951.
The bombings of Leuven (or Louvain in French/English/WW 2 usage)
are covered on the internet, although mostly in local Dutch/Flemish and more often than not a reference is made to the collision ND951 reportedly was involved in.
Since the bombings were around midnight and with the existing curfews for the population, I very much doubt if anyone other than some German military could have witnessed what may have happened in the air.
See e.g.
http://users.skynet.be/kkrol/Belang/bommen.html where also the bombing deaths of Belgians is discussed.
Under "Leuven, 12 mei 1944" there is a witness account, but as experienced from the cellar of an abbey.
Also see
http://www.aviationheritage.eu/nl/co...s-z-nd923-ko-c with pictures of the grave sites for the bomber crews of the two Lancasters that crashed at Wilsele near Leuven, including ND951.
Regards,
Leendert