for socialchange. he says that provers the enertain m industry can change attitudes about gun violence too. he doesn't think that's happening. with several violent offerings nominated for oscars this year. a 2013 study found gun violence in the movies has more than tripled since 1950. gun control advocate isn't convinced there's been any impact on gun tests. connection between the media and glorification of guns. >> reporter: it's enough of a concern that president obama signed an executive action in 2013 directing the cdc to investigate the relationship between media images and violence. what about the celebrity signing that recent letter to the president? actor liam neeson, we counted 20 founds where he brandishes a gun. jessica alb signed the letter. >> how many more movie theaters? >> he also appeared in this 2012 psa demanng gun laws alongside jamie foxx. he signed on to the star and django unchained. one of the entertain ms most powerful voices acknowledge the issue in 2014. >> i can't make one movie and go >> reporter: he's backed a sin city sequel and the hateful wait.