When one of the terrorists involved in the Paris shootings dropped his smartphone in a trashcan outside the Bataclan concert venue on Friday night, he wasn't worried about encrypting his text messages or stored documents. Why would he be? With a bomb strapped to his waist, he knew he was about to die.
But that telephone, and wiretaps on another, led police to announce Thursday that the suspected organizer of the shootings and a string of other attacks, Abdel Hamid Abaaoud, was dead.
The phone discarded by one of the terrorists contained an SMS sent to an unidentified recipient at 9.42 p.m. local time, moments before the shooting there began: "On est parti on commence" ("We're going in"), public prosecutor François Molins told a news conference Wednesday evening.
The phone also contained a detailed map of the interior of the concert hall, according to local media reports citing police sources.
The attacker's lapse in information security came too late for French security services to prevent the shootings, but it did contribute to the swift identification of three hideouts used in the days leading up to the attack. Two were already abandoned. but more than 100 heavily armed police raided the third on Wednesday morning.
Investigators used CCTV recordings, wiretaps, cellphone location information, search warrants, eyewitness accounts and data mined from existing intelligence reports to identify and locate the cars, phones, weapons and hideouts used by the terrorists to plan and execute the attacks, Molins said.
Cellphones can't work unless they regularly report their location to the network, so it knows where to direct their incoming calls and SMSs. Networks typically store that data for a few weeks or months for fault analysis or, as in this case, as a result of a legal obligation to retain the data for use in police investigations.
Tracking the location reports received from the telephone used to send the SMS led police to a hotel in Alfortville, on the outskirts of Paris, where they found two rooms had been rented Nov. 11-17 in the name of Salah Abdeslam, Molins said. Abdeslam is suspected of involvement in the attacks.
While technology didn't lead police to the other hideouts, it did allow them to confirm two tip-offs they had received from other sources.
One of those tip-offs prompted a search of an empty house in Bobigny, northeast of Paris.
The second suggested that Abaaoud, the suspected organizer of the attacks, was hiding on the top floor of an apartment building in Saint Denis, to the north of Paris, and not in Syria as previously thought.
Investigators analyzed telephone and banking data to confirm the information about Abaaoud, Molins said, before ordering an explosive and bloody assault on the building Wednesday morning by France's top SWAT team, RAID.
"Swatting" -- making false reports that will lead to the intervention of a SWAT team -- is a serious problem in the U.S., and with police forces on high alert in France, such reports could cause serious harm if acted on without restraint.
Over 100 police officers surrounded the building in Saint Denis before the assault began on Wednesday. At 4:20 a.m. local time, they attempted to blow the apartment door open, but it wouldn't move, losing them the advantage of surprise. In the shootout that followed, one of the apartment's occupants set off an explosive charge, killing herself. Another was later found dead on the floor below, pinned beneath a fallen beam.
Police worked through the night to identify the bodies, confirming Thursday morning that the dead woman was Hasna Ait Boulahcen, local media reported. Wiretaps of her conversations with Abaaoud led police to the apartment, the reports said, citing police sources.
Shortly after midday Thursday, the news arrived: Abaaoud was dead too, killed in the police raid. His body was identified by its fingerprints, a statement from Molins' office said.
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