This is not the first cover-up by a Western government of the Islamic nature of terrorism. It seems to be policy at this stage.
The article in French is at the News site, Le Figaro.Fr
A complete English translation can be found here.
An excerpt below:
The state agents of urban supervision center of Nice are stunned. "This is the first time we are asked to destroy evidence, says a source close to the investigation.The center of CCTV and the city of Nice could be prosecuted for this and also the officers in charge of the device don’t have jurisdiction to engage in such operations. “The request is all the more astonishing that since the last Friday the SDAT sent its servers to recover the 30,000 hours of CCTV related to the events.A backup operation that will extend even on several days. "We do not know if giving a destruction order while we are in full backup is not going to affect the whole system,” the investigators say with concern.