'They weren't just sacrificing these animals, but they were torturing them first', said Randall Sullivan, visibly shaken by what he had witnessed.
'It seems as if pain and suffering are part of the experience, and there's no doubt there's a dark power in blood sacrifice.
'The next step would be human sacrifice', the American told MailOnline, 'and I frankly think these people have done it'.
'It was disgusting', said shocked Michelle Gomez following the gruesome ritual.
'The fact that they would do that to a defenceless animal is sickening, and makes me scared about the lengths they would go to in order to see the devil'.
Michelle, who comes from Austin, Texas was at the ceremony in an attempt to improve her own psychic powers, which she claims have helped her to locate the souls of over one hundred kidnap victims.
'It makes me scared for myself to think I've witnessed this. They need to stop these rituals', she said with tears in her eyes beside a burning pentagram which the satanists had used to summon Beelzebub.
'If they can kill an animal in the name of purification, what other lengths will they go to?'
The lakeside town of Catemaco on Mexico's Gulf Coast is a destination for many 'pilgrims' who come in search of spiritual experiences.
Enrique Vernon organises the annual mass at his ceremonial grounds on White Monkey Mountain to the west of the town.
'Our black magic stems from Native American Olmeca culture, and we are experts in calling upon the devil and his dark power', said chief shaman Enrique Verdon, who wears a dead anteater on his head.
'People come to our devil-summoning ceremonies when they want to achieve change in their lives', he told the MailOnline in his office decorated with figures of the skeletal Saint Death, pentagrams and pelts of exotic animals.
'Some come to ask Satan to give them success in the future, others come to get over their difficult pasts'.
'Our marriage is failing, and this is something we both have faith in', said Alejandro Montes, shortly before he and his wife smeared the blood of a sacrificed goat over their faces in an attempt to save their relationship.
The pair had travelled to Catemaco from Monterrey in northern Mexico in order to pledge their souls to Satan in return for a happy marriage.
'We've tried everything and this is our last resort', said Alejandro, whose extramarital affair had strained their union. 'I'm willing to put my soul on the line to prove my commitment'.
A total of eight people underwent the ritual last week. Many witnesses were present at the ceremony, including a number of international tourists who had come to Mexico specifically to witness the black mass.
Randall Sullivan, a visitor from Portland, Oregon had heard of the event through his involvement in spiritualistic circles, and had come to witness the spectacle.
'I want to know how these shamans work their magic', he said before the ceremony.
'They are the only people I've head of who can mix black and white magic, that's like mixing God and the Devil'.
'It's something very mystical', said Samuel Casella, an Italian tourist from Milan. 'I expect to see something incredible tonight'.
A total of eight satanic priests had come from across Mexico to conduct the ceremony below a full moon.
'We are all powerful individuals. Some are healers, others are destroyers', said Joyri Ra, a devil worshipper from southern Mexico who wears a necklace made of human finger bones.
'Tonight we are going to open the portal to another dimension so that those who ask to communicate with Satan will be heard'.
The ceremony began with a group of teenage girls, all dressed in black underwear, carrying the terrified sacrificial offerings along a candlelit path to the main altar: a font filled with burning charcoal onto which the waiting shamans would throw handfuls of putrid herbs.
'The girls must be virgins, and be both mentally and physically pure', said Roselia Belli, a 'black witch' who uses strong tobacco and piercing screams in her own exorcism ceremonies, for which she charges clients more than £200 an hour.
Those who had come to plead their cases to Satan were called forward and ordered to kneel before the shamans, who wrung the necks and removed the heads of chickens before pouring the birds' blood over the kneeling penitents' heads.
'The blood pumped from a still-beating heart is the purest form of energy', chief shaman Enrique Verdon told the horrified crowd.
'These animals have to die so that we can continue our spiritual work.'
'Their blood will be offered up to the dark powers', he said, shrouded by the thick smoke billowing out of the fiery altar over which the decapitated chickens were held once bled dry.
'We are calling upon Satan, the prince of the Earth, to appear before us'.
The sacrifice of animals for display has been outlawed in the state of Veracruz, but is nevertheless still widely practiced in the devil-worshipping communities of the rural areas where this ceremony took place.
'There's little we can do to stop them', Arturo Bermudez Zaruta, the chief of police for Veracruz state told the MailOnline in a telephone interview the next day.
'If these people want to make displays of cruelly murdering animals, they'll do it whether it's legal or not'.
'This sacred blood give us the energy and spiritual power we need to make our black magic', said Enrique Verdon, as he cut the throat of the final sacrificial offering: a screaming goat whose blood was collected in a bronze jar to be passed around.
'We encourage our visitors to take this blood, pumped from a still-beating heart, and rub it into their skin in the name of purity'.
In total, eight animals were sacrificed during the ritual.
Following the sacrifices, the shamans stood before a large burning pentagram and attempted to summon the devil through their chants, before descending with the new adherents of the black mass to an underground cave decorated with inverted crosses, animal carcasses and a large statue of Satan with an erect penis.
The eight shamans gathered round each individual penitent and swore oaths to the effect that their soul now belonged to Satan, and that if their promises to the devil were not upheld then their spirit would be forfeit.
The committee of shamans screamed 'Hail Lucifer!' following each new oath and prostrated themselves before the statue, over which the remaining blood from the sacrificial offerings had been poured.
'If you don't fulfil your promises to Satan he will take everything away from you', preached Joyri Ra as he wiped sacrificial blood from the statue onto the forehead of Alejandro Montes.
'You are taking on a serious dark curse'.
'I felt terrified during the entire process', said Alejandro, who took soul-binding oaths before the shamans and the devil statue that he would not be unfaithful to his wife again.
'But now that it's done I feel strong. I believe things will improve now'.
His wife, Gloria Espina, did not wish to be interviewed.
The dedicated black masses by the devil worshipping cult began in 1970. Held on the first Friday of March, they have grown steadily in both notoriety and popularity over the subsequent 45 years.