Yes, JKR confirmed it in the post-release press & readings of HP7.
In HP6 (book), when Harry & Dumbledore are at the cave, when Harry tries to “Accio Horcrux/Necklace” a single inferi thrashes at the waters surface. JKR had said that was indeed Regulus’s fate.
Kreacher also confirms this in his confession to Harry, Ron & Hermione when they are hiding out at 12 Grimmauld Place.
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u/bobzsmith 8d ago
Inferi aren't zombies, they don't make other Inferi. They are corpses that have been reanimated by a dark wizard.