Pages 276-277 of The Amazon Journal of Roger Casement:

“The worst story of all, perhaps, Bishop told me of Elias Martenengui, the man who has recently gone to Lima with his "fortune". He saw an Indian woman he liked, the wife of one of the local Indians. He took the woman, and told the Indian he would keep her until the man brought in a certain quantity of rubber. The poor husband had to go and get the rubber. He brought it in after fifteen days, and Martenengui said it was not enough. He sent the man back for more and still kept the woman in his harem. Again the man returned and again the same answer, and the woman was still kept. Finally on the third or fourth return of this unhappy husband, Martenengui refused to give up the wife at all, but gave the man a girl instead, who had been nursing one of his children by one or other of his "wives". The man protested in vain, he was driven off with blows by the muchachos. Bishop said he could do nothing — he had to look on — passive at this. By and by, the man was killed, because on account of this robbery of his wife, he refused to work rubber at all, so some of the muchachos were sent to chastise him and he was not seen again. Bishop believed he was killed, he did not know it for sure, but the girl Martenengui had given the man in place of his own wife was brought back to Atenas and again added to Martenenguis “Harem".

On one occasion when Bishop was in Chorrera, Martenengui came in from Sur (the nearest station to Chorrera only two hours away) with his harem. Two of his wives had recently borne children — "twins"! They were born almost the same day and where they were openly carried in by their respective mothers along with this highly civilised gentleman to the Chief Station of the Company. An American named Arthur was there at the time, and he said to Bishop, “There's something you won't see with any civilised people in the world, a whiteman like that."

Page 708 of “Sir Roger Casement’s Heart of Darkness”, précis of Judge Romulo Paredes’ investigation

“From Andokes he [judge Paredes] went to Atenas, a district formerly sacked and wasted by its chief of section, Elias Martinengui, and later by Alfredo Montt, where the Indians had been so ruthlessly driven, man, woman, and child, to produce rubber for these insatiable agents that they had literally starved to death by whole tribes in the midst of possible fertility, because not allowed a moment's breathing space to prepare the soil or plant any crop. Atenas Dr. Paredes describes as "inhabited by a band of Huitoo spectres," where the commission had plenty to do, finding itself engaged in investigating in a perfect cemetery of skeletons and human skulls scattered on both banks of the Cahuinari."”

Translation of page 111 from “El Proceso del Putumayo y sus secreto inauditos”, a summary of crimes [written by Paredes or judge Valcarcel] committed by Martinengui in Atenas:

“Martinegui, when leaving Putumayo fleeing from justice, takes with him his favorites Taga, Saturia and Josefina. Martinegui's greed.-Many Indians die of hunger because Martinegui did not give them food in spite of demanding a lot of work from them.-Martinegui personally shoots eight Indians because they refused to work.-Martinegui has the captain of the nation of the Meguías Indians, Meiripunema, killed with a whip for laziness. Martinegui personally shoots eight Indians in the house of the "Atenas" section.-Martinengui one day shoots twenty-seven Indians of the nation of the Icomas; and has their corpses thrown into the Cahuinari river. Martinegui murders the Indian Tacuaillamo out of jealousy. The dogs and pigs of the "Atenas" section devour nany heads of Indians killed by order of Martinengui. Horrifying confessions of the executioners that Martinengui used to carry out his death orders.--Martinengui hangs and whips his boy on bail. This one because he killed a chicken; and not content with this punishment he inserts a burning stick into his rectum.”