Analysis of information sources in references of the Wikipedia article "Γκουρού Αρντζάν" in Greek language version.
In that way, their good Pope died, overwhelmed by the sufferings, torments and dishonours. – Jerome Xavier, Letter to Gasper Fernandes in Lisbon, On the execution of Guru Arjan
He was the first Guru to have been born a Sikh.
The Mughal rulers of the Punjab were evidently concerned with the growth of the Panth, and in 1605 the Emperor Jahangir made an entry in his memoirs, the Tuzuk-i-Jahāṅgīrī, concerning Guru Arjan's support for his rebellious son Khusrau Mirza. Too many people, he wrote, were being persuaded by his teachings, and if the Guru would not become a Muslim, the Panth had to be extinguished. Jahangir believed that Guru Arjan was a Hindu who pretended to be a saint, and that he had been thinking of forcing Guru Arjan to convert to Islam or his false trade should be eliminated, for a long time. Mughal authorities seem plainly to have been responsible for Arjan's death in custody in Lahore, and this may be accepted as an established fact. Whether death was by execution, the result of torture, or drowning in the Ravi River remains unresolved. For Sikhs, Arjan is the first martyr Guru.
Jahangir, Akbar's son and successor, had ordered the execution. We know from Jahangir's own handwriting that he was jealous of Guru Arjan Dev's popularity and that a gesture from the Guru towards Khusrau, a son rebelling against Jahangir, had outraged him.