Details of Disappearance
William was last seen when he left his plumbing job at Smith Kline Beecham at 15th and Spring Garden Philadelphia, Pennsylvania at 2:30 p.m. on March 23, 1987. He got into his black 1983 Plymouth Turismo and drove away. Normally he would have gone to his home on Beaver Run Road in Nockamixon Township, Pennsylvania, but he never arrived there and has never been heard from again.
When his friends couldn't get in touch and went to his home to check on him, it appeared as if he had left in a hurry. His guns were still in their gun cabinet and there was a pot of spaghetti on the stove, and nothing was missing except his car, which has has not been recovered.
William disappeared just two weeks after he'd sued his younger brother, Frederick William Muller. Their mother had died and William was suing Frederick for control over her estate, including the farmhouse and seventeen-acre property on Ferry Road where they'd grown up. He believed Frederick was running a narcotics operation out of that house and wanted to put a stop to it. After his disappearance, the lawsuit was dropped.
In 2000, Frederick was arrested on drug charges; he'd been using the farmhouse to manufacture methamphetamine. Police stated he was a suspect in the 1998 murder of a Philadelphia police officer and in the "probable murder" of his brother. The officer's severed arm was found in a trash bin in Trenton, New Jersey two days after his disappearance; the rest of his body was never found. No one has been charged in either the officer's death or William's, but in 2001 Frederick pleaded guilty to the drug offenses.
William was newly divorced at the time of his disappearance, but had three daughters and other relatives living in the area. He was declared legally dead seven years after his disappearance and his estate, worth $235,000, was disbursed to his relatives.