A group in Mexico identified as Los Mata Zetas, or the Zetas Killers, has made a video vowing to kill members of the notorious drug cartel that recently decapitated an Internet commentator and hanged disemboweled bloggers from a bridge.

Members of Los Mata Zetas wear ski masks in a new video in which they threaten to kill members of the Zetas drug cartel. (Image via YouTube)

The video’s speakers say they are part of a vigilante force, working “of the people and for the people.” But the Associated Press reports that they probably are from a group linked to the rival Sinaloa cartel, because of “the language and style of the declaration.”

In a statement Monday night, the Interior Department said the attorney general’s office “has opened an investigation into the videos that express the aforementioned ideas and are circulating on the Internet.”

Watch the video below: