By Michelle Ward Trainor and Nina Biddle  11/14/2015 AT 03:25 PM EST  It was a scene no 14-year-old should ever have witnessed.  On Friday, Mathieu L. was at a friend's house for a sleepover, so close to  that his friend's building became a first aid area to treat victims of the attacks that broke out that night, his mom tells PEOPLE.  "It was a protected courtyard. The police ushered the victims into that area. The mother of the boy who Mathieu was staying with took in a young man who had escaped the concert hall and was in shock," says Sandra Nagel, a 44-year-old German arts administrator living in Paris.  Nagel, who asked that her son not be identified by his last name, says she was in "constant touch" with her son by phone while no one was allowed in or out of the area.  At least 80 people were killed in the Bataclan, which was assaulted by four gunmen during a coordinated series of terror attacks in the capital that left at least 129 dead and 352 injured,  The Islamic State (ISIS) has reportedly claimed responsibility for the attacks, which President Francois Hollande  Cards, candles and flowers are placed in front of the Carillon cafe in Paris on Nov. 14, following a series of deadly attacks in the city the night before.  That night, while the tragedy was still unfolding, Nagel says that everyone in the building – about 50 flats – came down to the courtyard to help.  "It was a good place to keep the lightly injured people," she says, adding that people brought "blankets, whatever food they had, phones for people to use.  [Eagles of Death Metal] came there," she says.  And one of those heroic helpers was Mathieu, who had been following the attacks on TV and who went down to the courtyard around midnight.  "We offered these people water, Coke, soft drinks and some yellow covers that my friend's mother had as it was cold," he tells PEOPLE, speaking in French. "My friend's mother took the first of these refugees upstairs to the apartment. He was alone and in shock and had blood on his T-shirt. Many of them were crying or in shock. Most of them were with friends.  "At first I was in shock myself, but then I realized what was happening ... the whole situation was terrible. It makes you feel impotent."  But Nagel says she couldn't be more proud of her son's assistance.  "Maybe what Mathieu will take from this is that he did something constructive, something that was better than sitting upstairs worrying."
How a 14-year-old boy and other Parisians acted heroically to help the victims in the wake of the horrific attacks