Witnesses told officers the 61-year-old "was alone on the balcony taking a cigarette break when he may have suffered a medical emergency resulting in his fall from the balcony". He won an Emmy in 2015 for his work on the HBO movie Bessie.
Emswiller fell from a balcony he was standing on during a break in filming.
He was taken to UPMC Mercy hospital near Mt. Lebanon, Pa., in serious condition, but his status worsened after arriving.
Emswiller was involved in the sound production of You Are My Friend, which was shooting a scene in Mount Lebanon.
Bystanders heard a odd noise at one point, went to investigate, and determined that Emswiller had fallen from the balcony.
An award-winning sound mixer died after falling from a balcony on the set of a new movie starring Tom Hanks as the children's television presenter Mr Rogers.
Emswiller was rushed to the University of Pittsburgh Medical Center for treatment but succumbed to his injuries.
The Marielle Heller-directed film - now without a name but previously developed under the title You Are My Friend - was shooting a scene in the Pittsburgh suburb of Mt. Lebanon, just south of the city.
The film is set the explore the relationship between Rogers and a cynical journalist sent to profile him, who finds his life changed as a result.
He also sports greying hair and eyebrows for his portrayal of the beloved star.
Hanks was reportedly present when Emswiller fell, and left the site sometime after.
"Mister Rogers" Neighborhood" began airing in 1968 and captured the hearts and imaginations of children across America.
Rogers, who died in 2003, was the subject of the documentary "Won't You Be My Neighbor" released earlier this year.