For roughly five months during 1975 pets and farm animals were found slaughtered by unknown creatures on the island of Puerto Rico. In most cases strange screeches, hums and the sound of flapping wings were heard before and after the attacks. Residents began to report strange birds that around the island.

The mystery of the Chupacabra did not restart again for nearly twenty years, when on March 31, 1991 two Palmarejo residents heard their pet Dobermans howling. The couple noticed a humming sound throughout their home and was too afraid to initially help their pets until one of the canines shrieked. After stepping onto their patio to investigate, the couple saw two creatures- each about three or four feet tall with gray skin, a slit-like mouth, big heads and a small nose- standing before them. The figures dashed away as the couple searched for their pets. They found two dog carcasses, each with its insides pulled out from the eye sockets. Every single organ and muscle mass had been removed, as were the eyes. The couple threw the bodies into a nearby ravine, where authorities could not relocate them.

Police officers claimed to see a strange beast near Orocovis, Puerto Rico. The characteristics of the encounter were similar to that of the March 31 meeting, but the officers noted the creatures had yellow eyes. As the officers gave chase to the fleeing animals, they became nauseated and terminated their hunt. On March 26 at about 6 AM, a UFO researcher reported a similar creature that exhibited chameleon-like characteristics. The Chupacabra reportedly shifted from purple to brown to yellow.

As the reports continued to flow, they grew more fantastic. As Daniel Pérez reported to Jorge Matrín, he had also seen a very exotic creature. The five-foot tall animal floated down from the sky using six inch fins and landed using powerful legs. Pérez claimed to see the same creature the very next morning but kept the sighting to himself and his wife. Soon, other people began to report the same creature. At one point, a local resident claimed to have captured a Chupacabra and held it captive for a short time before it escaped.

Martín soon compiled a general description of the creature, which included "strong coarse hair all over its body ... the remarkable ability to change colors" and "two small arms with a three-fingered clawed hand and two strong hind legs ... to enable it to run and quickly leap ... over twenty feet in a single bound." Other reports have given the Chupacabra everything from wings to slime.

The creature's origin is and has been a mystery since the very first sighting. Investigators have suggested theories from genetic engineering by the United States government to aliens. José Soto, the mayor of Canóvanas, helped lead a search party into the Puerto Ricon jungles to find the creatures. Some suggest that not only did Soto find a Chupacabra, but also with the help of United States officials, he captured and sent it to a facility within the United States.