Raised in Clifton, New Jersey, Seda was the second oldest of six children. His first expectations about acting were that he might get a part as an extra. An instinctive actor who oozes masculinity that creates the sexual danger of which male movie stars are made, but also possessing just the right dash of sensitivity, Seda won the role in "Gladiators". From there, he played a tough street kid in "Zebrahead" (1992) and a Dominican hoodlum in Brian De Palma's "Carlito's Way" (1993). More recently, he was Jose, one of the tortured inmates, in Terry Gilliam's futuristic "12 Monkeys" (1995). He won further critical applause for his work as a gangbanger with a brain tumor who takes a doctor hostage in Michael Cimino's little-seen "Sunchaser" (1996) and as a co-worker and rival in love to Leon in "The Price of Kissing" (1997).
Seda's early TV credits included episodes of "NYPD Blue" and "New York Undercover", on which he played a boxer. (According to some sources, he allegedly auditioned for the role series regular Michael DeLorenzo won). He was a cop killer whose trial is disrupted in "Mistrial" (HBO, 1996). Seda made guest appearances as an undercover detective on NBC's acclaimed drama series "Homicide: Life in the Street" (NBC) in 1996 and joined the series as a regular in the fall of 1997. Seda reteamed with director Darnell Martin for the premiere episode of the HBO drama series "Oz" (1997). As hotheaded Dino Ortolani, the actor delivered a mesmerizing portrayal of a tough lifer in a brutal prison environment who meets a gruesome death.