No one knows how the Martian Heat-Ray works (besides the fact that it manages to scorch people), but the narrator is willing to give us some theories anyway.
(By, the way, this chapter is a little confusing, but it seems to tell us what happened in Chapter 5 from a different perspective.)
People from the neighboring towns come to see what all the fuss is about. As the narrator notes, young people use this news as an excuse to go out and flirt, just as they would use any news to go out and flirt.
Police try to keep the crowd back, but there are only three police and maybe 300 people in the crowd, so our money is on the crowd.
Earlier Stent and Ogilvy had telegraphed a nearby military barracks to ask for some soldiers to come out and protect the Martians from the crowd, but the army hasn't shown up yet. This is what folks in the lit biz call irony.
The Heat-Ray kills some people, but it misses others. The crowd stampedes like "a flock of sheep," and they end up trampling "two women and a little boy" (1.6.10). Interestingly, this is much more specific than the info the narrator gives us about who got killed by the Heat-Ray.