Thomas was born in California in 1867; the son of Patrick and Catherine Flannelly, both born in Ireland. His parents appear to have emigrated to the U.S.A. in the 1850s and settled in San Mateo County in 1859 where they prospered. The retired couple resided in Redwood City.
Thomas inherited a dairy farm from his father a few miles outside Redwood City on the San Mateo road. Unfortunately, Thomas was not a hard worker and spent most of his time relaxing in the Redwood City saloons. As the farm declined, Thomas decided that he could engage a business partner to run the farm while he continued a life of leisure. His disappointed father objected to the proposed arrangement and decided that his favours had been abused, taking steps to evict the son and regain control of the farm
On 26th October 1897, after being served a notice to quit the farm, Thomas confronted his 62 years old father in his bedroom and the pair had a heated exchange. Thomas later claimed that his father had drawn a pistol from beneath his pillow; in any event, Thomas killed his father with three gunshots in the head and heart.
Thomas fled back to the farm on horseback but was soon cornered by a posse led by Sherriff William McEvoy. Refusing to surrender, Thomas exchanged fire with the posse and wounded the sherriff in the left arm. After being shot six times and running out of ammo, Thomas was finally captured by the posse and jailed.
The sherriff died from blood poisoning two days later and Thomas narrowly escaping lynching by an angry mob when quick-thinking deputies staged a fire alarm in Redwood City to distract the mob while Thomas was secretly transferred to the jail in Santa Clara.
His trial in San Josť started on 8th March 1898 and attracted a lot of media attention. He was convicted and transferred from Santa Clara County to San Quentin Prison on 22nd March 1898 and scheduled for execution by hanging on 27th May 1898. After a number of appeals (funded by a contraversial inheritance) he was eventually executed on 29th June 1900.
[his portrait is illustrated above; courtesy of San Quentin execution record, with special thanks to Bob Fitzer, historian of San Francisco Police Department]