Is owning a "Desert Eagle pistol" supposed to be a one-phrase commentary on the mans character or mental stability or something? How is that even relevant.
Desert Eagles are generally seen in media as garish, over-the-top, and "extreme". Countless films and videogames reinforce this.
It's a way for the media to invoke a subtle connotation. Basically, to the average reader it's a euphemism for "power-crazed nutjob".
To me, it just means the guy has really poor taste.