He was an immensely fat glutton.
Elijah Willie was the baron of Willie ville, one of the more powerful baronies in the Southeast. He was an immensely fat glutton who believed in genetic purity - he ensured the purity of his bloodline by engaging in incest with his daughters and granddaughters. He also kept a mutie zoo, a place with the most unique muties he could find, and used other muties as slaves. He was killed by one of his daughters after the ville was overrun by stickies and he refused to kill her to spare her from them (Skydark).
The baron was killed by his own Grand Daughter/Wife when he refuses to kill her to save her from a horrible death at the hands of the invading Stickie army. She used a Ruger Redhawk to shoot Willie in the stomach, killing him.