The truth is that violent crime rates have been dropping steadily: http://www.wanttoknow.info/g/violent_crime_rates_reduction "Did you know that violent crime rates of 2010 were 1/3 the rates of 1994?"
Some theories about why violent crime has declined so sharply: http://www.theatlantic.com/features/archive/2015/02/the-many-causes-of-americas-decline-in-crime/385364/
Some think removing lead from gasoline and stopping its use in paint helped reduce crime since it attacks key parts of the brain in growing children: http://www.motherjones.com/environment/2013/01/lead-crime-link-gasoline
But what about crime in terms of race?
FBI, arrests by race 2012: https://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2012/crime-in-the-u.s.-2012/tables/43tabledatadecoverviewpdf
FBI, arrests by race 2013: https://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2013/crime-in-the-u.s.-2013/tables/table-43
Fact checking claims about race and crime: http://www.tampabay.com/news/politics/fact-checking-claims-about-race-crime-after-ferguson/2208263 This site makes an important point: people are killed by people they know, by and large:
According to the U.S. Bureau of Justice Statistics, 93 percent of black homicides were indeed committed by other blacks between 1980 and 2008. In 2012, the most recent data posted on the Web, the figure was 91 percent.
It's important to note that whites were almost equally likely to be killed by other whites. According to government data, 84 percent of white homicides were committed by whites. This was true between 1980 and 2008 and in 2012.
Experts have stressed that this is not surprising because most homicides occur among people who know each other.
More on racially based statistics: http://www.nytimes.com/2014/09/08/opinion/charles-blow-crime-bias-and-statistics.html?_r=0
In conclusion, if you are making a good faith effort to understand why the death of some black people are national news but white people killed by black people is not as often the focus, consider that the normal course of events is for a black killer to be immediately arrested and locked up and for a white victim not to have their personal history combed through for reasons why they don't count as real victims. The opposite is usually the case for black victims of white killers. The ideal would be a justice system that treats all killers and all victims the same. In the case of rape, again most rape occurs between members of the same race and in fact, the majority of rapes are by people known to the victim.