A man from Los Angeles claims that he witnessed aliens fleeing from a UFO after it crashed landed in the desert - and he has a piece of the spacecraft to prove it.

Jose Padilla was just a nine-year-old boy growing up in San Antonio, New Mexico, when he and his friend discovered the 'avocado-shaped' UFO.

To this day, he swears that what he witnessed was real. 

The encounter occurred while the two boys were horseback riding in the desert just 13 miles from the Trinity nuclear test site, Robert Oppenheimer and other members of the Manhattan Project detonated the world's first nuclear bomb in 1945.

The encounter occurred that very same year, and at first, Padilla thought the sound of the crash was just another bomb test, he told CBS News Los Angeles. 

'I told my friend, 'it must be another test from the bomb' and he said, 'no, it's not a bomb, look at the smoke coming out of the ground,'' Padilla said.

Upon closer inspection, the smoke appeared to be coming from a crashed aircraft.

Then, all of a sudden, three extraterrestrials emerged from the aircraft and began 'sashaying and running in circles,' he said. 

But Padilla wasn't afraid of these creatures. 

'They had crashed at my father's ranch, and they needed help,' he said. 

Over the next ten days, the military cleaned up the wreckage while Padilla and his friend watched from a nearby ridge, despite being warned to stay away.

'We were hiding behind cactuses,' he said.

When the soldiers took a break from cleaning up the wreckage, Padilla and his friends entered the aircraft.

The 'extraterrestrials' were gone, giving Padilla the perfect opportunity to extract a souvenir from inside. 

He pulled a small 'dial' off the wall, brought it home and hid it in his garage. 

Frontier Analysis, a chemical testing lab based in Ohio, analyzed the artifact in 2015. Their report revealed that it was made of aluminum mixed with silicon and copper, CBS Los Angeles reported.

This mix of metals is commonly found in engine parts, and the report stated that the isotopic ratios were terrestrial.

But an extraterrestrial source for the metals could not be ruled out, the report stated.

'No one knows what it is,' Padilla said.

The years passed, and Padilla moved from San Antonio to Rowland Heights, an unincorporated area of Los Angeles, California, and quietly raised a family.

But he always held onto that strange artifact from his childhood.

In 2012, Padilla and the friend who was with him when he witnessed the UFO were interviewed by investigative journalist and UFO researcher Paola Harris. 

At the time, Harris was investigating a claim by the son of World War II army pilot William Brophy.

Brophy's son told Harris that one of his father's last missions was to fly over the area that Padilla claims the UFO crash landed in. During one such flight, he saw two young boys on horseback, Harris told CBS Los Angeles.

She believes those two little boys were Padilla and his friend.