Legally? He was operating legally by going through the administration element of selling a vehicle in Germany. And this on the back of apparently abducting, raping and killing a small child.
It all makes sense now.
I don't know what the diagnostics are regarding Brueckner but his proven record contains examples of psychotic behaviour including the abuse of children.
Were I you I would not glibly dismiss the fact that there are individuals who are perfectly capable of performing the basest of crimes described by you, against children or even geriatric women while presenting a normal persona to everyone else around them.
Rapists and murderers don't have it stamped on their foreheads, they look and behave pretty much like everyone else, that's how they get away with it.
The best that investigators can do is to look for a profile and from my reading of like individuals Brueckner ticks every box and then some on that recognised sheet. Much as police investigators seem to acknowledge by making him prime suspect in the crimes against Madeleine.