Detectives called to the United Artists Riverview Stadium theater in South Philadelphia found Cialella in the complex still carrying the weapon - a .380-caliber handgun - in his waistband, a police spokesman said.
"(It) is really scary that it gets to that level of violence from being too noisy during a movie," Lt. Frank Vanore said Friday.
The victim's name was not released, but Vanore said the 31-year-old man from suburban Yeadon was hospitalized in stable condition after the shooting.
A theater manager referred calls Friday to Regal Entertainment Group spokesman Dick Westerling, who did not immediately return a phone message.
Cialella was awaiting arraignment on charges including attempted murder, aggravated assault and a firearms count. He remained in custody without a lawyer. A call to his home number Friday rang unanswered.
Police could not confirm what movie was playing in the theater, but The Philadelphia Inquirer reported that it was "The Curious Case of Benjamin Button."