The trouble began a little before February 25, 1975, when a Puerto Rican newspaper first reported the strange animal deaths in the small town of Moca. In Moca's Barrio Rocha, fifteen cows, three goats, two geese, and a pig were found with puncture marks on their bodies, indicating a sharp object of some sort had been inserted into them... and all autopsies showed that the animals were missing every last drop of blood. Despite these two interesting details, police apparently tried to blame the deaths on dogs; meanwhile, the newspapers dubbed the unknown threat el Vampiro de Moca, the "Moca Vampire." By March 7, when a cow was found dead in Moca's Barrio Cruz with penetrating wounds on its skull and scratches around the wounds on its body, the death count had risen to over thirty animals. One theory going around was that the unknown creature was a supernatural bird of some sort, a theory based on one woman's report of a strange bird pecking at her rooftop and issuing a terrifying scream.
On March 12, a man named Luis Torres and his son and daughter witnessed something they described as looking like "The lights on a police cruiser" spinning in the night sky on the outskirts of Moca; Torres connected this noctural UFO sighting with the Moca Vampire by stating the object had been flying over fields in which some of the strangely killed animals had been found... and so theories shifted to the idea of the unknown creature possibly being an alien. By March 15, when a farmer lost thirty-four chickens to the Moca Vampire during the night, the animal death count was up to ninety victims in the two week period since it first manifested.
Around this time, Luis Torres killed two Puerto Rican boas, with each snake unusually large at over six-feet-long. Torres claimed to have captured the two snakes as they "stood ready to attack a 600-pound heifer." The local news media immediately blamed the strange animal deaths on the two snakes, and declared the problem ended... but on March 18, two goats were found drained of blood on the farm of a man named Hector Vega. The goats had puncture marks on their necks; and whatever made the marks came back the next night. In the morning Vega discovered seven goats injured, ten more killed, and a further ten goats that were just plain missing. By this point the Senate Agricultural Commission got involved in the matter, talking to the farmers and local law enforcement, which resulted in Senator Deynes asking the Superintendent of Police to "re-double his effots in getting to the bottom of the situation," which he felt could not have been caused by an animal.
On March 23, the strange killer struck again; and the nature of the attacks became weirder still. Felix Badillo discovered a ten pound piglet dead in its pen with no signs of a struggle, missing an ear and with a large hole on the side of its head... despite the presence of Badillo's watchdog, which had neither growled nor barked during the night. An expert noted the cut on the ear looked surgical in origin rather than animal made.
On March 25, a man named Juan Muniz claimed to have been attcked by a "horrible creature covered in feathers," while returning to the Barrio Pulido of Moca. He said he saw the strange creature, and then threw stones at it to try to frighten it away; instead it flew at him, and Muniz took cover first in some bushes, then at a neighbor's house. An armed group was unable to locate the strange 'bird.'
By April, reports of strange animal deaths started to turn up on farms all across the island of Puerto Rico, even as the police tried to find human perpetrators and the press tried to find rational explanations. On April 2, eight goats and a dozen rabbits were found dead in Corozal. Isauro Melgar, owner of the animals, mounted an all night watch on the following evening with a group of armed neighbors, and spread poison on the ground to protect his rabbits. They stayed up until three in the morning... but sometime after the group disbanded for the night, more animals were killed. Melgar then started all-night watches. On April 5, Melgar and his companions were suddenly deafened by a sound that appeared to be everywhere in the countryside; at the same time, a strange figure was seen running through trees away from an open pasture. They discovered later that four more goats had been slain.
In addition to the strange animal deaths, sightings of UFOs reported over Santa Rosa and Cerro Gordo. A giant cigar-shaped object with retangular portholes emitting yellow light hovered 1500 feet above a home in the suburb of Cupey for forty-five minutes... long enough to guarentee a lot of witnesses. The following morning scorch marks were found by investigators at a spot the object had been seen to briefly land.
On May 13, a man in Corozal encountered a "round-headed, hairy-tailed and large-eyed creature" that growled like a small dog; and around the same time in Moca, three roosters, a rabbit, and five goats that belonged to the municipal treasurer all turned up dead, drained of fluids. As the killings continued and seemingly spread, the reports of UFOs also increased. In May three unknown objects, two resembling stars, flew over the town of Fajarado; witnesses clearly stated that the objects were neither a natural occurrence nor something made by humans. On May 17, at nine-thirty at night, large glowing balls of light, house-sized glowing crafts, and a dark object with a red light on top were seen to perform strange maenuvers very low in the skies over Rio Piedras, and San Juan.
On June 25, twenty-five farm animals just outside of Isabela were found dead, drained of blood; sometime after that fourteen fighting cocks in Yauco were found in the same condition. The activity of the "Moca Vampire" decreased as the Summer wore on, and no more deaths were reported after July 1975.