Normally,
Normally, at a real airline (one that has SOPs that are taught, evaluated, and reinforced), the cabin crew does have the authority to command an evacuation. However, these instances are limited to cases that obviously require an evacuation such as: after a crash with major structural damage, (it is obvious the pilots are incapacitated and evacuation is warranted), a fire, dense smoke, or any situation that poses imminent danger and the pilots cannot be contacted. Things of this nature....
In the Bus, there is a cockpit switch that has two positions: one, where only the cockpit can trigger the evacuation alarm, the other where either the purser or the pilot(s) can trigger the alarm. My old company's SOP (from which I retired) was to position the switch to 'cockpit only'.
Never, at my old airline, have we had a problem where the cabin crew initiated an evacuation on their own without communicating first with the cockpit. But, I came from a 'legacy carrier' where our cabin crew are fairly bright....not someone who was sacked from Burger King.
However, we have had instances where passengers panicked and bailed out on their own. One time, during push back and engine start, a CFM 56 torched a bit. One idiot saw this, and before you know it, the over-wing exit was opened and people were jumping out.
As the ticket prices lower (due to the attributes of deregulation), we see more idiots traveling.
We really can't say what happened in this instance, as news reports are usually wrong. At my university, the students who were sharp typically majored in engineering, science, or math. The ones less gifted usually majored in band or journalism. So, it never surprised me that reports related to aviation are typically incorrect.
Fly safe,
PantLoad