Subaru died suddenly

Dear Car Gurus,
Hi! I hope you all are having a nice day. I was too, till my car suddenly make a
screeching noise and just died on the road. It sounded like I drove over some
garbage thrown on the road, like a cardboard box or something. I have a 2003
Subaru Forester with 147010 miles. I have had it for one and half years. The
seller had the transmission job done two years ago. It has a new water pump,
spark plugs, tune up. The only thing that is not working is my driver side
window. I was going to get it replaced this weekend.
I am not sure what happened. I am up to date on oil change, maintenance, and
all the essentials. The car engine seemed slightly loud when I started it this
after noon. I went to the grocer store, turned the A/c on and was on my way
home. I was driving on the main road and the car stalled. I checked and made
sure the fluids are full, Tried to start the car to drive it out of the main road, no
luck.  
The car is in my parking lot now. When i tried to start it, the check engine and
the battery lights are on and the car starts, but the engine is making a hell of
scratchy noise and the engine seems to be accelerating on its own.
I love my car and do take a good care of it. I appreciate your input regarding
this matter. Could not reach the mechanic due to the long weekend. Will tow it
to the garage on Tuesday. I want to know what exactly do you think has
happened. All I can say is we are going through a heat wave in CT. I park the
car outside in the parking lot. Please suggest what to do? Thanks
Happy Labor Day!