Madonna caused people to walk out of her concert in Colorado this week by brandishing a false gun.
The second song in the singer's current 'MDNA' set list, 'Revolver', sees her brandish a replica firearm, but the act was not welcomed when she performed in Denver, less than 15 miles from the site of a massacre in June this year.
Concert-goer Aaron Fransua, 25, said: "We're dancing and all of a sudden people started realising what the song was.
"We all just stood there. Everybody who was around me all had shock on their face. I heard a lot of 'wows'."
Twelve people, including a six-year-old girl, were killed and a further 58 injured in the massacre, when loan gunman James Holmes opened fire on a crowd waiting outside a cinema. The community is still reeling from the incident, but Madonna remains firms.
A representative said the scene is an integral part of the show, adding to remove it would be 'like taking out the third act of [Shakespeare's play] Hamlet."
Madonna has previously defended the use of guns in her stage show, saying they are metaphorical.
She explained: "It's true there is a lot of violence in the beginning of the show and sometimes the use of fake guns - but they are used as metaphors.
"I do not condone violence or the use of guns. Rather they are symbols of wanting to appear strong and wanting to find a way to stop feelings that I find hurtful or damaging.
"In my case it is wanting to stop the lies and hypocrisy of the church, the intolerance of many narrow minded cultures and societies I have experienced throughout my life and in some cases the pain I have felt from having my heart broken."