In the video you can clearly hear them yelling “fuego,� or fire in Spanish, and earlier someone calls out for gasoline, and apparently the same man in grey pants, white shirt, and white cap sprays petrol / gasoline on the girl twice : initially before he (probably the very same man) sets her on fire (with a burning piece of paper), and later again after she had almost stopped moving (after burning, writhing and screaming for a minute). The 2nd time the same man added more petrol onto her, you can hear the girl scream again and actually continue writhing violently (indicating she was still alive when he added the 2nd douse of petrol). At the end of the video, after having burnt for several minutes, you'd notice her hand was still twitching, indicating that she still didn't yet die immediately after both burnings.
Article and video :
http://therightscoop.com/horrific-angry-mob-beats-and-burns-alive-girl-in-guatemala/