It wasn't the work of Muslim extremists in cahoots with the Al Qaeda terrorist network, the human-rights activist says.
If it was the work of Muslim extremists, it was only in conjunction with the Indonesian military.
"The widely held opinion is that Muslim radicals were responsible for this," says Rumbiak, who is in Toronto on a mission to expose military brutality in his home province of Papua.
"That might be true. But people have to look further and study the relationship between the military and this group. They couldn't do it themselves.