I suggest the creation of a not-for-profit organisation, provisionally titled "Gamers Against Real Violence", to facilitate the gaming industry's response to this issue.
The mission statement of this organisation would be something along the lines of:
We make, play and enjoy computer games that are violent, and that may even glamorise, glorify or trivialise violence. However, we a steadfast in our condemnation of real-world violence. We look forward to the day that violence only exists in fictional media, and we will support causes to this end.
Developers would be allowed to display the GARV logo and mission statement on splash screen before and after games, and on box art etc, if they are members of GARV.
Members would be required to take action to the stated aims of the organisation, for example by donating to relevant charities (e.g. Amnesty International), sponsoring independent research to explore the impact of violent gaming, supporting rehabilitation, etc.