Mid/rear Seats Assembly problems of the 2007 Toyota RAV4

On March 29, 2016, I was driving to work in the far left lane when a gentleman driving a green pickup truck come rushing up beside me. He was waving at me pointing down at the right front side of my Toyota. I thought that maybe I was driving on a flat tire and didn't realize it so I rolled down the window. He yelled as he was still pointing down at the front of my Toyota "your car is on fire". He got ahead of me and I pulled over to the right shoulder of the freeway. He got out of his truck and ran back to my 2007 Toyota Rav4 and said "MA'am, you better get your purse and things and get out, your car is on fire". At that time, smoke was pouring out somewhere up front on the passenger side by the tire. I got my things and we moved to the back of my Toyota when at that time, it went up in flames. I took care of that vehicle because I can not afford another. My last oil change was in November 2015 with only 50035 miles on the vehicle. When it was last inspected, everything was fine. So I am not understanding how this happened. Tires were about a year old as well. Car just don't catch on fire driving down the freeway. On April 4, 2016 a friend and I took a drive to my burnt vehicle and she could not believe that was my Toyota. And I could not believe I had walked away without any injuries. There is no engine, no dashboard, no steering wheel, no front seats, and no back seats. All burned! how could this happen?.