In this example, the topic sentence for Main Fact 2 is that a person who texts too much can put others at risk. This would be the main fact that would include all of the supporting details. The supporting details that I would expect to see in this paragraph would be those that expand on this idea. For example, I would expect to see an explanation of the ways in which other people are put at risk, and of the ways in which damage can be caused to others. For example, the author could include how texting can make you distracted and increase your reaction time. He could also talk about how texting means that your hands are busy, which might make it more difficult for you to manouver if necessary.
