A spokesperson broke the news to THR Sunday, saying the actor passed away Saturday night in L.A. after a brief battle with cancer. Unclear what sort of cancer he might've been battling, or when he was diagnosed -- but it sounds like it was kept fairly private.

While de los Reyes will perhaps best remembered for his role as Antonio Vega on "One Life to Live" -- on which he was featured in 287 episodes -- video game fans probably recognize him too ... as he voiced villain Raul Menendez in the "Call of Duty" series.

He voiced Menendez -- a main and recurring character -- for a total of 4 'COD' installments ... including the famed 'Black Ops II,' where he debuted as the big bad for years to come.

de los Reyes had an impressive résumé outside of that as well. In addition to his work on 'OLTL' and 'COD' -- he had also memorably starred in shows like "Sleepy Hollow," "All American," "The Rookie," "Reed Between the Lines, "Promised Land," "Four Corners," "Valley of the Dolls," "ER" ... as well as guest starring on "Law & Order," "CSI," "The Mentalist" and more.

He had also been in a handful of films ... like "Nixon," "In Search of a Dream," "The Cell," "Cayo," "Salt," "LA Apocalypse," "Amelia 2.0," "Hot Guys with Guns" as well as others.

de los Reyes is survived by his wife, Sherri Saum, their children and other family. He was 56.