Brakes failed

Friday morning my brakes went out on me. I was pulling out of a parking space and my car was puttering (as if it was going to turn off) then I was pulling out of the parking lot, but when I stepped on the brake pedal, it wouldnt go down! So i put it in reverse ( i was going about 5mph)and circled around and just put in park and turned it off. I didn’t even think to use the Ebrake. My son was in the back seat so I just tried to stop it automatically.
I’ve been reading that doing that might have ruined my transmission. Please help!!
-Samantha

its a 2001 ford focus se

Is the check engine light on?

The brakes are power assisted by means of a booster that runs on a vacuum that’s there when the engine is running. If that vacuum is missing or the car isn’t running, you really have to jamb down on the pedal to get the car to stop.
The car will stop but will take a lot more effort than normal.
Since you say the car sputters, I wonder whether you have a vacuum leak somewhere. The car would run badly and the vacuum to the brake booster would likely be missing.
Look around for hoses that may have popped off. Get some car starter fluid, start the car and if it sputters, spray a little around hoses. If the engine speed goes to normal and stops sputtering when you spritz the starter fluid at certain spots, you likely have a vacuum leak in that area.
Btw, the brake booster is a large looking round part that usually sits up against the firewall (the wall between you and the engine) on the driver’s side. There’s a rubber hose attached to it. Check that hose.

Of course, it could also be that the car is just running badly and the brake booster not getting a vacuum is a side effect but we have to start somewhere.

I agree with RemcoW. I believe you had brakes, just without a power assist because of some sort of engine problem. All drivers need to understand that you still have brakes in this situation, but you’ll need to press very much harder on them.

With regard to your question about ruining the transmission by sticking it in park while it was moving, it is possible to damage the parking pawl (I believe it is called) in the transmission by doing that, but if you were going very slowly when you did it, and the car stopped and stayed stopped, then the parking pawl probably survived OK. If there is a next time, you will use the parking brake.

The OP needs to find out what caused her engine to “putter”.
As was said, she never actually lost her brakes, and only lost the power assist for the brakes as a result of some obvious engine problems.

Rather than have the real issue get lost in the fog–so to speak–if you resolve the engine problems, you will resolve what you mis-perceived as the loss of your brakes. Yes, you should be concerned about how you abused the transmission, but as Manolito stated, there was likely little or no damage.

Right now, the OP needs to have her engine problems diagnosed and fixed before there is a repeat of this incident, and/or before she winds up being stranded. Being stranded with an infant is not a good thing, so the OP needs to get the car to a competent mechanic (NOT Midas, Meineke, Monro, Sears, Pep Boys, AAMCO, or a tire shop) a.s.a.p.