Mildred tells Montag that she thinks that a man called McClellan hit Clarisse in his a car and killed her. However, when Montag presses her, she says she is not entirely sure if Clarisse actually died. It is only when Montag asks his boss that he finds out for sure.

Beatty tells him that Clarisse's family had been on the government radar for a while due to what he calls their anti-social behavior. Normally he says that they "nip most of them (the ones as young as Clarisse) early," but it seems she was too far gone for them to be able to change her. He doesn't tell Montag how she died, but he does say that "the poor girl's better off dead."

Montag thinks he has in insight into how Clarisse dies when he is on the run and a car full of teenagers tries to mow him down. He wonders if they were the ones that tried to kill Clarisse. He is in no doubt that they are out to kill him because they turn around and try to hit him again.

Clarisse has a profound effect on Montag and is arguably the catalyst for his change. It is Clarisse that reminds him of the person he is and can be and opens his eyes to what is happening in the world. When she dies, Montag stops going into work and begins to seriously question everything that is happening around him.

In Part One, Montag develops a significant friendship with his teenage neighbor, Clarisse McClellan. She is an enthusiastic, genuine person, who is the catalyst that makes Montag question his personal happiness. Montag begins to cherish his brief moments and conversations with Clarisse McClellan, until one day she disappears. After not seeing Clarisse for seven consecutive days, Montag begins to worry about her well-being. When Montag asks his wife if she has seen Clarisse throughout the neighborhood, Mildred casually mentions that she forgot to tell him that Clarisse got ran over by a car and died. Montag is both shocked and horrified after finding out his close friend passed away and wonders why Mildred didn't tell him sooner. Mildred simply responds by telling Montag that she forgot. Mildred is too preoccupied with her Seashell radios and parlour walls to remember something as significant as Clarisse's death. Mildred is also a shallow, callous individual and does not fully understand the nature of Montag's friendship with Clarisse. 

In Fahrenheit 451, Clarisse dies, but Bradbury does not describe this event in the text. Mildred informs the reader of Clarisse's death. In Part Two, when Montag notes that he has not seen Clarisse for four days, Mildred declares that she is "gone" and that she was "run over by a car." Clarisse's family has also moved out and left the area. When Montag asks why she did not tell him sooner, Mildred says she "forgot."

Clarisse's cause of death is confirmed in Part Three. When Montag is running away from the Hound, he is almost knocked down by some joyriding teenagers. This prompts him to wonder if they were responsible for killing Clarisse, but this notion is neither confirmed nor denied by Bradbury.

The first time we hear of what happened to Clarisse is when Mildred tells Montag "Whole family moved out somewhere. But she's gone for good.  I think she's dead." (pg 47) She goes on to tell him that Clarisse was run over by a car four days ago.  She wasn't sure,but she was pretty sure. 

Later, when Beatty is talking to Montag he says that Clarisse was a time bomb.  Her family had been feeding her subconscious and she kept asking questions.  That could lead to unhappiness.  So, "she is better off dead".(pg 60)  He says that luckily people like Clarisse do not appear often but that the government now knows how to "nip most of them in the bud.." (pg 60)

Clarisse has been "nipped in the bud" as they say and is dead.

The pages I have sited are in my edition of the book, but they should be somewhere close to that page.

Why does Clarisse have to die in Fahrenheit 451? Why did the author make Clarisse die?

Clarisse doesn't have to die in this novel. There are several reasons, however, why it makes sense for Clarisse to die.

First, Clarisse functions as a plot device: she is one of the "drops" of water falling on Montag (along with Mildred's suicide attempt) that leads him to begin questioning the way he has been living his life. Once she has fulfilled that function, she in some ways becomes an encumbrance in the novel: after all, an older, married man like Montag can only have a friendship with an underage girl for so long without raising uncomfortable questions, no matter how pure his motives might be. Killing Clarisse gets rid of the problem of a relationship that really can't develop.

Second, killing Clarisse illustrates that this is a society in which people like her can't expect to survive. The society doesn't want thinking, questioning, vitally alive people like Clarisse rocking the boat and raising uncomfortable issues about the culture in which they live. As Beatty says:

The girl? She was a time bomb. ... She didn't want to know how a thing was done, but why. That can be embarrassing. You ask why to a lot of things and you wind up very unhappy indeed, if you keep at it. The poor girl's better off dead.

Why does Clarisse have to die in Fahrenheit 451? Why did the author make Clarisse die?

In some respects, Clarisse seems like a martyr of sorts, whose life and death serves to reveal the full selfish nihilism on display in this society which Bradbury imagines. From the very beginning of the story, she is characterized as a free-spirit, and someone vibrantly and actively engaged in her own existence (which is rare in a world where most people have been reduced to the status of passive consumers, even within their own lives).

Her death, as an earlier contributor has already pointed out, illustrates just how deeply wrong and monstrous this society is. Clarisse was run over by a car and, furthermore, the larger society does not seem to even care that she was killed. Indeed, when Montag finds out about the incident from Mildred, Mildred admits that she had not told him because she'd forgotten about it. She's too caught up in her own self indulgence. What results is a powerful indictment of the society that Bradbury has envisioned, and the kind of hedonistic lifestyle that lies at its center.

Why does Clarisse have to die in Fahrenheit 451? Why did the author make Clarisse die?

Each character in a story is included to serve a purpose, whether it is to move the plot forward or to serve as an antagonist to the main character. Clarisse serves several purposes in this novel. She is a teenager, representing innocence and imagination, and is the antithesis of what Montag's society is all about. She provides Montag with the motivation to question his society and his own role in furthering the goals of that society. Clarisse and her family represent what Montag's society could and should be. They talk to one another and care about each other. They aren't lonely or alienated from one another.

Why does Clarisse have to die? Her death emphasizes all that is wrong with Montag's conformist society. Bradbury uses her to show the inhumanity of the society in his novel. If a society would kill a sweet, innocent girl, what does this say about it? Her death intensifies Bradbury's message to the reader.

In Fahrenheit 451, why does Clarisse vanish from the book?Why does she have to "die" in the book she was a good character.

In my opinion the purpose of Clarisse's death was three-fold.

1. Clarisse had to die because she was all that remained of what we readers understand as good. This is a dystopian novel. Thus, for us to find the society as completely dysfunctional, we needed to see that one lasting piece of truth and goodness destroyed. This spurs our passion to act once the reading is done.

2. Clarisse's death only further perpetuates the motives of Montag to seek out and either liberate the society or himself from the society. When he learns of the typical way she might have died, it enrages his drive to continue his journey.

3. This is a little off topic, but I think very relevant. My students often read into Clarisse as a potential love interest for Montag. For her to have continued to exist, readers might lose sight of what Bradbury was really trying to point out. He had no intention in commenting on romance and how it develops. His intentions had to do with making society think about the fact that technology and the absence of reading can destroy us unless we are careful.

Why Clarisse has to die in Fahrenheit 451?Did the Author remove her from story so that he could introduce other characters like Faber?What does her death signify?

Clarisse has to die, in part, to demonstrate the madness and control of the government, as well as the threat she represents to them.  It is also important simply for the sake of the story in that Montag's epiphany about what he does for a living, and what their society has become, is not possible without someone as innocent and joyous as Clarisse paying the ultimate price for her free thinking ways.  It is Montag's critical mass moment.