The media does seem to have a great effect. Want to die, kill someone, and be famous? Mass shooting. Media swarms and your face is plastered on everyone's TV screen all over the country. As it is, all the news stations hone in on everything about the shooter and give minor condolences to the victims. If we focused on the victims of the shooting and downplayed the shooter as much as possible or even ignored him altogether, I'd be willing to bet we'd see a sharp decline in mass shootings because the incentive of being made famous as quickly and easily as possible is taken away.

Gun laws are only as strong as the weakest link. Houser had domestic violence history, had a history of destructive crime, had been involuntarily committed, had been denied a conceal carry permit, and he still legally purchased a gun at an Alabama pawn shop which he used to kill two people in a different state.

What is increasing is the ability of people like Houser and Roof and those before them to find like-minded individuals on stormfront, 4chan, reddit, or wherever else who post violent reactionary rhetoric that encourages them. Certain media influences are getting increasingly ridiculous, and ultra-conservative political groupies stopped pretending to be reasonable a while back. These cultural influences are what these folks are stewing in.

Better medical care would surely help, if these people weren't convinced to turn it down or opt out of it.

Source: http://www.bjs.gov/content/pub/pdf/fv9311.pdf

I'm copy-pasting the most relevant information, in my opinion. I'm also formatting this a bit with the quotation bars to maybe make it easier to read. I can change it if people don't find it easier on the eyes. Anything I don't copy-paste will be italicized above the line.

Firearm-related homicides declined 39%, from 18,253 in 1993 to 11,101 in 2011.

Nonfatal firearm crimes declined 69%, from 1.5 million victimizations in 1993 to 467,300 victimizations in 2011.

Firearm violence accounted for about 70% of all homicides and less than 10% of all nonfatal violent crime from 1993 to 2011.

About 70% to 80% of firearm homicides and 90% of nonfatal firearm victimizations were committed with a handgun from 1993 to 2011.

From 1993 to 2010, males, blacks, and persons ages 18 to 24 had the highest rates of firearm homicide.

In 2004, among state prison inmates who possessed a gun at the time of offense, less than 2% bought their firearm at a flea market or gun show and 40% obtained their firearm from an illegal source.

Males, blacks, and persons ages 18 to 24 were most likely to be victims of firearm violence

In 2010, the rate of firearm homicide for males was 6.2 per 100,000, compared to 1.1 for females homicide for males declined by 49% (from 12.0 per 100,000 males in 1993 to 6.2 in 2010), compared to a 51% decline for females (from 2.3 per 100,000 females in 1993 to 1.1 in 2010). The majority of the decline for both males and females occurred in the first part of the period (1993 to 2000). Over the more recent 10-year period from 2001 to 2010, the decline in firearm homicide for both males and females slowed, resulting in about a 10% decline each.

In 2011, the rate of nonfatal firearm violence for males (1.9 per 1,000 males) was not significantly different than the rate for females (1.6 per 1,000). From 1994 to 2011, the rate of nonfatal firearm violence for males declined 81%, from 10.1 to 1.9 per 1,000 males. During the same period, the rate of nonfatal firearm violence against females dropped 67%, from 4.7 to 1.6 per 1,000 females. As with fatal firearm violence, the majority of the decline occurred in the first part of the period. From 2002 to 2011, the rate of nonfatal firearm violence for males declined 35%, while there was no statistical change in the rate for females.

In 2010, the rate of firearm homicide for blacks was 14.6 per 100,000, compared to 1.9 for whites, 2.7 for American Indians and Alaska Natives, and 1.0 for Asians and Pacific Islanders. From 1993 to 2010, the rate of firearm homicides for blacks declined by 51%, down from 30.1 per 100,000 blacks, compared to a 48% decline for whites and a 43% decline for American Indians and Alaska Natives. Asian and Pacific Islanders declined 79% over the same period, from 4.6 to 1.0 per 100,000. Although blacks experienced a decline similar to whites and American Indians and Alaska Natives, the rate of firearm homicide for blacks was 5 to 6 times higher than every other racial group in 2010.

In 2004, among state prison inmates who possessed a gun at the time of offense, fewer than 2% bought their firearm at a flea market or gun show, about 10% purchased it from a retail store or pawnshop, 37% obtained it from family or friends, and another 40% obtained it from an illegal source . This was similar to the percentage distribution in 1997.

Here's page 8 of the .pdf showing nonfatal victim-offender relationships.

According to this report, their source on fatal shootings doesn't include victim-offender relationships.

However, I did stumble upon another report by the BJS. It doesn't single out firearm statistics, but homicides as a whole. http://www.bjs.gov/content/pub/pdf/htius.pdf#page=48

Most victims and perpetrators in homicides are male. Both male and female offenders are more likely to target male victims than female victims.

For the years 1976-2005 combined, among all homicide victims, females are particularly at risk for intimate killings and sex-related homicides.

Female victims are more likely than male victims to be killed by an intimate or family member. Male victims are more likely than female victims to be killed by acquaintances or strangers.

End of data

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Personal opinion

I don't think that we can reasonably conclude that men are driven by sexism to kill women. Overwhelmingly, men and women both kill men. The wife/girlfriend is more likely to be killed by the husband/boyfriend, but his motivations aren't necessarily known. It doesn't mean that he's a sexist. He could have issues (clearly) with the way the relationship is going, such as they're breaking up, one or the other is cheating, etc.

Overall, we've seen a marked decrease in gun violence in the past 20 years. I think that we've glossed over that due to the increase in media, especially the popularity of the internet. These things put the spotlight on issues like gun violence, sexism, or racism, so it seems like things are worse, but in reality, we're just looking at these issues harder.