The Swiss Federal Prosecutor’s Office report on the decision to discontinue the investigation said the first two wingsuit jumpers in the party landed without incident.
However, it said Byrne collided with the mountainside and suffered fatal injuries.
The report said proceedings would be discontinued if there was insufficient evidence of any criminal suspicion, such as knowingly placing life in danger.
“The fatal crash was, with a high degree of probability, attributable to a situation from which there was no escape, resulting from insufficient lift and the low altitude above the ground,” it said.
“There are no indications in the present case of any criminal acts by third parties that contributed to the crash, or of a pre-existing technical defect in the equipment used that contributed to the crash.
“The proceedings are therefore discontinued.”