On arriving at his house, where the principal conspirators waited for him, it was determined to kill the marquis on the following Sunday, as they had not been able to put their design into execution on the festival of St John213 as they at first intended. On the Saturday immediately preceding, one of the conspirators revealed the circumstances of the plot in confession to the curate of the great church of Lima. The curate went that same evening to communicate the intelligence to Antonio Picado, secretary to the marquis, who immediately carried the curate to Francisco Martinez de Alcantara, the marquises brother214, where the marquis then was at supper together with his children215. On being informed of the urgent business on which they came, the marquis rose from table and retired to another room, where the curate informed him of every thing he had learnt respecting the conspiracy. The marquis was at first considerably agitated by his intelligence: but after a moments reflection, he said that he could not credit the story, as Herrada had been with him only a few days before, and had conversed with him with much humility; for which reason he was convinced that the man who now brought this intelligence had some secret end to serve, and had invented this story to assume merit. He sent however, for his lieutenant, the doctor Juan Velasquez216 meaning to consult with him; but as Velasquez was ill in bed, the marquis went to his house, and told him all that he had heard. Velaquez used every argument to convince him that the story was false, and that he had nothing to fear. Taking up his rod of office, he declared that no one dared to revolt so long as he held that badge in his hand, and that the marquis might rest in security. He may be said in some measure to have kept his word; for when the Almagrians came next day to kill the marquis, Velasquez made his escape over a window, and took his rod of office in his teeth, that he might use both his hands to assist himself in his descent.

In spite of all these assurances the marquis was somewhat alarmed, insomuch that next day, being Sunday the 26th June 1541, he determined not to go to church, and had the mass said in his own house. After church, the doctor Velasquez and captain Francisco de Chaves, who were the principal persons in the colony, went along with several other persons to visit the marquis. Having paid their visit, they all retired to their houses, except Velasquez and de Chaves who remained to dine with him. After dinner, between twelve and one o'clock, when all the attendants of the marquis had retired to their dinner, and the whole city was quiet, Juan de Herrada and ten or twelve of his associates all armed sallied forth from the house of Almagro, which was not more than three hundred paces from the palace of the marquis, between which were part of a street and the whole breadth of the great square. On coming out into the street with their drawn swords, they exclaimed, "death to the tyrant who hath slain the judge sent by the emperor to execute judgment upon him." They used these words, and went thus openly, to induce the inhabitants to believe that their party was numerous, so that no one might take measures to oppose them. Besides this, the conspirators believed that there was no time for any one to interpose to prevent the execution of their purpose, and that it would either be accomplished, or themselves slain in the attempt, before any effectual succour would arrive. On their arrival at the palace of the marquis, one of the party remained at the gate with a bloody sword in his hand, who cried out repeatedly, "The tyrant is dead! the tyrant is dead! " This had the desired effect, as several of the inhabitants who hastened to the palace on the alarm, being convinced that the marquis was already slain, retired again to their houses.

In the mean time Juan de Herrada and the rest of the conspirators rushed up the stair towards the apartment of the marquis, who, being alarmed by some of the Indian servants, desired de Chaves to shut the doors of the saloon and the hall, while he retired to put on his armour. De Chaves was so much confused, that instead of fastening the doors he went out to the staircase demanding the reason of the noise; on which one of the conspirators wounded him. "This, said he, is not the usage of a friend," and immediately drew his sword, but was soon overpowered and slain. The conspirators immediately rushed into the hall, whence ten or twelve Spaniards who were there made their escape by the windows: Among these was Velasquez, who, as has been already mentioned, took his rod of office in his mouth, that he might use his hands the more readily in making his escape by the window. The marquis was at this time in his chamber, employed in arming himself, attended by his brother de Alcantara, two other gentlemen, and two pages. Seeing his enemies so near, the marquis was unable to fasten the clasps of his cuirass, but advanced courageously with his sword and buckler to defend the entry to the chamber, in which he was bravely assisted by those who were along with him. He defended himself for a considerable time successfully, encouraging his brother and the rest by his voice and example. At length the Almagrians slew de Alcantara, on which one of the pages took his place beside the marquis. The Almagrians, being afraid lest succour might arrive, resolved to make a desperate effort, for which purpose one of the best armed among them forced in at the door and made room for the rest to enter, who now attacked the marquis and his faithful companions with such fury that he was soon exhausted with fatigue and hardly able to handle his arms. At length the marquis received a mortal thrust in his throat, and falling to the ground called out in a loud voice for a confessor. Soon losing all power of speech, he made the sign of the cross on the floor with his finger, which he kissed and expired. Besides his brother, the two pages were likewise slain. Of the Almagrians, four were killed, and several of the rest wounded.

When the marquises death was made known, above two hundred men who waited the event, declared themselves loudly in favour of Don Diego, and went about the city arresting and disarming all who seemed to favour the party of the marquis. The conspirators went out into the street waving their bloody swords, and Herrada made Don Diego ride on horseback through the city of Lima, proclaiming him as governor of Peru. The palace of the marquis, and the houses of Alcantara and Picado the secretary were pillaged, Herrada assembled the cabildo of the city, and obliged them to acknowledge Don Diego as governor, under pretence that the elder Almagro had been appointed by his majesty to the government of New Toledo, with succession to his son or to any person he might appoint as his successor. The conspirators likewise put to death several persons who were particularly attached to the late marquis, and gave up their houses to be plundered by their own partizans. It was melancholy to behold the misery and desolation of the wives and children of those who were thus massacred, and whose houses were pillaged of every thing valuable, as they went about the streets bewailing their forlorn condition.

Some obscure persons217 carried or dragged the dead body of the marquis to the church, where no one dared to give it burial, till one Juan Barbaran and his wife, who had been servants to the marquis, obtained permission from Don Diego, and buried the marquis and his brother as well as they could. They were obliged to hurry over the ceremony as quickly as possible, having hardly time to clothe the body in the habit of St Jago, of which order he was a member, and to put on his spurs according to the usual manner of burying the knights of that order; as they were informed that some of the Almagrians were hastening to the church to cut off the head of the marquis to affix it to the gallows. Barbaran himself performed the ceremonies of the funeral, at which he was sole mourner, and defrayed all the expences from his own funds. He next endeavoured to provide for the security of the children of the marquis, who were concealed in different parts of the city of Lima, now under the absolute controul of the Almagrians.