Ex-MLB prospect Brandon Martin has been convicted of killing three men -- including his disabled father -- with a baseball bat back in 2015 ... and could now face the death penalty.
27-year-old Martin was a promising young shortstop in the sport ... and was a first-round pick of the Tampa Bay Rays in 2011.
Martin killed his 64-year-old dad, 58-year-old uncle and a 62-year-old alarm installation worker at their family home in Corona, CA in September 2015.
The details are gruesome ... Martin beat the men with a black bat inscribed with his name before stealing the alarm installer's truck and fleeing the scene.
The following day, law enforcement spotted the pickup truck ... and Martin tried to escape before ultimately ditching the vehicle, breaking into a house and jumping from a 2nd-story window in an attempt to get away.
Martin was charged with 3 counts of first-degree murder ... as well as a number of other charges stemming from the incident. He pled not guilty and the case went to trial.
A jury started deliberating earlier this week ... and after 4 hours, Martin was found guilty on all 7 counts, including all 3 first-degree murder charges.
The conviction makes Martin eligible for the death penalty ... which is being sought by the District Attorney.
The penalty phase of the trial starts Monday ... when Martin's fate will be determined.