India, June 23 -- The grieving father of Argentine YouTuber Gaspar "Gaspi" Prim, who was killed alongside American singer Oliver Tree and four others in a helicopter crash, says he believes "it was an attack."

Ricardo Prim, who owns a bookstore in Puerto Madryn said his 23-year-old son died in a "very unjust way" in the June 14 crash in Rio de Janeiro in Brazil, Argentine outlet Clarin reported.

"It's not known whether it was an accident or an attack," he said. "I didn't know the American singer who was with him, Oliver Tree, but I'm receiving a lot of information and I believe it wasn't an accident. For me, it was an attack."

Ricardo did not explain what made him suspect an attack and authorities have said the cause of the crash is st...