Derek Harrison, 35, was among five people shot dead at the Walter Rossler Co., a refinery inspection firm in Corpus Christi, Texas, on April 3, 1995. The attacker, identified as former employee James Simpson, entered the office and methodically shot Walter Rossler, his wife Joann Rossler, Wendy Gilmore, Richard Tomlinson and Harrison. Simpson died at the scene.

Simpson had left the company seven months earlier. Authorities have not established a motive for the rampage, and investigators did not name any other suspects or file criminal charges in connection with Harrison’s death. The killings were described as one of the city’s bloodiest crimes and occurred days after the murder of Tejano singer Selena Quintanilla, deepening local grief.

If anyone knew Derek Harrison, his routines, or had information about Simpson’s departure from the company, please share what you know.