这个短文有点说不清楚状况.
第一,开头的有一个人来到了超市,文章中并未表明是否这个人就是那个贼.
第二,偷完水,这个贼占在门口准备坐着车走,这个车是公车还是出租车也未说明.
故只能给出以下的翻译.
One day,a guy came to the supermarket when Tom and Bob were there,too.They saw a thief stealing a bottle of water and walking out.The thief stood outside the supermarket and was ready to go.At this time,Tom and Bob saw a policeman.Then they came to tell the whole thing.Finally,the thief was caught and his tear fell down.