In March, Gutierrez, 27, was found guilty of involuntary manslaughter for mistakenly loading a live round into a revolver Baldwin was using on a Santa Fe, New Mexico, movie set
The source said Hoffman was found dead after a 911 emergency call from a friend of the actor. The source gave no further details.
The New York Times, citing a law enforcement official, said investigators found a syringe in Hoffman's arm and an envelope containing what was believed to be heroin.
Hoffman, 46, won the Academy Award for Best Actor for the 2005 biographical film Capote, and received three Academy Award nominations as Best Supporting Actor.