Liege shooting: Two police and passer-by dead in Belgium but there's no discernible motive per the police, prosecuters and BBC News

This BBC report http://www.bbc.co.uk/news/world-europe-44289404 into the recent shooting in Liege is quite incredible:

'A man has shot dead two police officers and a passer-by in the centre of the eastern Belgian city of Liège before being killed himself.

... 

Details are still emerging and there is no indication yet as to the man's motive.

"We don't know anything yet," a spokesperson for the Liege prosecutor's office told the AFP news agency.

... 

Police sources quoted in local media said the man was heard shouting Allahu Akbar ("God is greatest" in Arabic).'

So police sources said the man was heard shouting "Allahu Akbar" but apparently there is still no indication as to the man's motive.

This is like some sort of sick parody.