Hassan, 23 years old, sent his friend Fatima a series of WhatsApp messages to explain his plans, according to Spanish daily El País.
"We’re going to Syria. Don’t tell anyone, OK?" he messaged Fatima.
When she asked her friend why he was going to Syria he replied simply, "For Allah."
"Are you being serious?" Fatima asked her friend, to which Hassan (not his real name) replied, "Yes. It pays well. It’s very dangerous...I’m going to give your number to someone so you’ll be the first to know if something happens to me."
After their conversation, Fatima called her mother, who had worked with many young people in Barcelona who had flirted with radical Islam. The girl's mother then contacted police.
The next time Hassan called Fatima, she recorded the conversation.
He told her that he was travelling to Syria with a friend and some other young people and that "everything was free". He explained that he didn't have a passport and was going to be given false identity cards.
Fatima also found out that it was not the first time Hassan had travelled to Syria and the only other person he had told about his plans was his mother, who told him, "If you've got to go, then go. Goodbye."
It dawned on Fatima that during the last few months she had lost touch with various Moroccan friends. She started to suspect that perhaps they too had gone to Syria to join Isis.
Fatima called the police and told them all about the phone call, showing them the WhatsApp messages, as well as photographs of her missing friends.
Catalonian officials have revealed that since 2013 at least 20 people living in Catalonia have travelled to the Middle East to join Isis.
Hassan told Fatima that he was persuaded by a man in a shop to visit a mosque, where he met other young men who like him, had neither family nor resources to help them get by.
"They look for that profile," says Fatima’s mother, who knows many young Moroccans who have come to Spain illegally at 16 or 17 years old. "Many live badly, very few work, some steal," as did Hassan, Fatima confesses.
"They enroll them as soldiers of Islam and pay them a lot of money. That’s what attracts them."
In messages sent to Fatima, Hassan says, "We eat well. We wear designer clothes and we don’t have to steal."
In the last message Fatima received from Hassan, he said he was still in Europe, training for his upcoming trip to Syria.
In December, a Madrid mosque was revealed to be the base of a jihadist terrorist recruitment network, which aimed to recruit people to send over to fight for Isis.