There's not enough details to know why this happened, but there are usually only a few causes.
I'm curious how/why it would go after two grown men, and succeed.
It can. And sometimes results in cyclists and hikers being stalked.
That doesn't usually end with an attack though.
A grown man fighting back should send a cougar running.
There are some rare instances where that isn't true. This may be one, so I'm curious what was different.
If the cougar attacks, fight back aggressively and try to stay on your feet.
They way I imagine it, you're never on your feet in this situation. Maybe I'm overestimating the cat.
See people keep calling Australia deadly but we don't have Mountain Lions and Bears.