That is one reason and a very good one, 762. That's why it was enshrined in the US Constitution.
I should also add that, if the woman, whose name I will not mention, had a gun, she could've fought back. The murderer, a police officer, didn't buy his gun legally. He got it from the government, and even if he couldn't have gotten it through the straight and narrow, he could have stolen one from evidence, requisitioned one, or gotten one in other various illegal ways. The government took her ability to get a gun away, though, as she was a law abiding citizen. Her death may have been unavoidable, he could've killed her without her having seen it coming but she could've also fought back and won. In the end, no-one knows whether she would have lived or died if she had a gun, but the fact is, she would have had a chance.
Edit: Again, I have to ask, why grant the usage of firearms to police officers and not the law abiding citizen? And why can public comfort (Not safety, as England/Wales is proof that, before and after the extreme restriction and near-banning of guns, crime rates and numbers actually went up relating to guns being used in them) override personal rights?