He had been arrested in Manila for inciting rebellion against the Spanish, and after he was released on the importunities of some Dominican priests, he returned to Cagayan.
He was said to have committed atrocities upon his fellow natives for refusing to rise up against the Spaniards.
He soon controlled the countryside, and the Spanish eventually found themselves besieged.
They fought successfully against the rebels, and captured and executed several leaders under Magalat.
Magalat himself was assassinated within his fortified headquarters by his own men, who apparently had been promised a reward by the Spaniards.