aka Indagine su un cittadino al di sopra di ogni sospetto

Fabulous film from Elio Petri scoring a best foreign film Academy Award in 1971 and featuring a terrific performance from Gian Maria Volonte, surely one of the best Italian actors ever.
I've been wanting to discuss this film for a while now, mainly concerning the ending, so here goes.
At the end of the film Volonte, only credited as 'Police Inspector', is in his house and is seen lying on his bed. He's disturbed by the arrival of a delegation of officials, higher ranking members of the Police, and is given a dressing down for his crime and even though he admits to the murder is absolved by his peers and is off the hook. As soon as he's been let off the film cuts to him lying on his bed where he is seen to be waking from a nap, he gets up and looks out the window to see his peers arriving at his house... The film then ends.

My take on it is that the aforementioned visit and his subsequent 'letting off the hook' for his crime was a figment of his imagination, he is afterall barking mad, and he dreamt it all. When he's shown getting up off the bed and the Police arriving he's now in reality and he's about to get busted.
Any thoughts? Hope that made sense!