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ORLANDO (CBSMiami/AP) — Thirty minutes into the worst mass shooting in modern U.S. history, the gunman called a 911 operator and claimed responsibility for the massacre at a gay nightclub in Orlando.

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Transcripts released Friday by the city of Orlando show Omar Mateen’s first call to police from the Pulse nightclub and also disclose his conversations with police negotiators.

During his first call, Mateen pledged allegiance to the Islamic State group and said: “I want to let you know I’m in Orlando and I did the shooting.”

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A dozen minutes later, a police negotiator called him. Mateen tells the negotiator the U.S. needs to stop bombing Syria and Iraq, adding, “They are killing a lot of innocent people.”

The June 12 nightclub attack claimed 49 lives and seriously injured 53 others.

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