Didier Lallement said Friday that no track was excluded on the deadly attack that took place Thursday at the Prefecture of Police of Paris.

The police chief of Paris assured Friday not to exclude "no hypothesis" in the aftermath of the murderous attack perpetrated Thursday by an officer of the Prefecture of Police who killed four of his colleagues.

"Our police lucidity leads us to strictly exclude any hypothesis at this stage," said Didier Lallement, while the investigation opened by the Paris prosecutor has so far not retained a terrorist qualification. "We were touched in the heart but we are still standing," said the prefect.