A rare one-horned rhino at a national park in Nepal suffered and died under the hands of poachers.

According to Telegraph, the male one-horned rhino was shot in the head and left to die after poachers gouged its horn.

The incident which occurred on a rainy eve last Friday is the first rhino brutality that took place at the national park ever since anti-poaching measures were implemented by the park three years ago.

In an interview with Skynews Australia, Ram Chandra Kandel, chief warden of Chitwan National Park, explained that the poachers likely used a silencer because no one near the site heard any gunshots. She also noted that the spiteful crime seemed to be well planned.

"It appears that they were planning this for a long time and were waiting for an opportunity to strike," Kandel explained.

Since it was raining and also thundering when they committed the crime, no one noticed the poachers. The corpse of the poor one-horned rhino was only found the next day, Saturday.

"The poachers fled with his horn and tail and left the animal in a pool of blood," Kandel lamented.

Meanwhile, Nurendra Aryal, another spokesperson from the park told AFP that a team is already investigating the incident and security had already been tightened at the district borders.

Mongabay reported that despite the recent incident, Nepal has made substantial progress in rhino conservation. The outlet said that due to their conservation and anti-poaching efforts, the rhino population went up from 375 in 2005 to 645 in 2015.

Illegal trade in animal parts remains a lucrative business in the international black market. Among the most coveted animal parts used by Chinese as traditional medicine ingredients are rhino horns, elephant tusks, donkey hide and tiger parts.

As per the World Wildlife Fund, the greater one-horned rhinoceros is the largest of the three Asian rhinos. It has a single horn between 20 to 60 centimeters long. Aside from illegal poaching, rhinos are also threatened by pressures of human encroachment.