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An explosion lights the front of a kosher supermarket as French police special forces launch their assault to free hostages. Photograph: Reuters

From the father who hid his toddler inside a supermarket refrigerator to the employee who texted tactical information to police from beneath a sink, authorities praised the quick instincts of survivors in the sieges that gripped France on Friday.

At the printing business north-east of Paris one employee took refuge “under a sink in the canteen” upstairs after the brothers believed to have carried out the Charlie Hebdo massacre stormed in, Paris prosecutor Francois Molins told reporters.

The employee – a 26-year-old graphic designer, according to a source close to the investigation – had been “terrified”, Molin said.

But overcoming his fear as he remained undetected, he began communicating with police outside via text message, sending them “tactical elements such as his location inside the premises” as well as what the attackers were saying, a source said.

The brothers – identified as Cherif and Said Kouachi, on the run since they are believed to have slaughtered 12 people at the weekly magazine’s offices in Paris on Wednesday – had been cornered there after a firefight with police which Molins said left Said with a minor neck wound. They still had arms including Molotov cocktails and a loaded rocket launcher.

The brothers had taken the store manager hostage but later released him after he helped Said with his wound as the second man hid upstairs, said Molins.

Another source said the hidden employee was also able to communicate with a family member via text.

Some 40 kilometres away, shortly before 1pm, a father called Ilan and his three-year-old son were at a kosher supermarket in Vincennes when Amedy Coulibaly, believed to be an ally of the Kouachi brothers, burst into the store and pulled out a Kalashnikov.

The father and son quickly hid in the supermarket’s refrigeration unit, two relatives told AFP. At least three other people were with them, according to sources close to the investigation.

Ilan, in his thirties, removed his jacket and wrapped his son in it to keep the toddler warm. Hidden in the cold, they and the other hostages remained in the refrigerator for nearly five hours.

Ilan’s mother realised quickly that her son and grandson were hidden and decided not to try to contact them, even by text. Instead she gave Ilan’s mobile phone number to law enforcement, who were able to use it to track the location of the man, his son and the other hostages inside the store.

This knowledge, according to the prosecutor, may have contributed to their survival when police finally stormed the store and killed Coulibaly.

A man holding a child is among hostages rushed away by police from the kosher grocery store. Photograph: Michel Euler/AP

Meanwhile, in Dammartin-en-Goele, police launched their assault on the printing works and reached the upper floor to free the hidden employee, a source said.

The employee, unharmed, was taken to police headquarters, where he was quickly reunited with his family, another source close to the case said, adding that the young man was “shocked but OK”.

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