"I'm still processing it," Banks explained during an appearance on Today on Wednesday. "I really am in shock."
Hoffman joined the film franchise as Head Gamemaker Plutarch Heavensbee in The Hunger Games: Catching Fire. The Oscar winner starred opposite Banks, Jennifer Lawrence, Josh Hutcherson, Woody Harrelson and Donald Sutherland.
"He is an absolutely amazing actor, respected by everyone and part of our family at The Hunger Games," the 39-year-old actress, who portrays quirky District 12 escort Effie Trinket, said. "We will miss him terribly, and obviously, [we're] really upset for his children and his partner."
"It's just a tragedy," Banks added.
Hoffman's role in The Hunger Games: Mockingjay—Part 1 was "substantially complete" at the time of his death, a source close to the production confirmed to E! News shortly after his death.
The actor, who was found dead in his New York City apartment on Feb. 2, had seven days remaining to shoot The Hunger Games: Mockingjay—Part 2, the source added. Hoffman's tragic passing "will not affect" the film's scheduled release dates of November 21, 2014, and November 20, 2015, respectively.
"[Philip Seymour] Hoffman was a singular talent and one of the most gifted actors of our generation," Lionsgate, the studio behind the Hunger Games franchise, said in a statement obtained by E! News. "We're very fortunate that he graced our Hunger Games family. Losing him in his prime is a tragedy, and we send our deepest condolences to Philip's family."
Hoffman's autopsy was inconclusive, a spokesperson for the New York City Medical Examiner's office confirmed to E! News on Wednesday. Additional tests, including a toxicology study, must be conducted in order to determine what caused the actor's death.
A rep for Hoffman confirmed to E! News that a private funeral will be held in New York City for family and close friends, adding that a separate memorial service is also in the works for later this month.
(E! and Today are both part of the NBCUniversal family.)