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Florida gunman Nikolas Cruz wrote online that he wanted to be a “professional school shooter” before he killed 17 people at Marjory Stoneman Douglas High School nearly four years ago, according to testimony at his penalty trial.

Broward County Sheriff’s Detective Nick Masters described for jurors Cruz’s disturbing online activity that began seven months before the Feb. 14, 2018, killing of 14 students and three staff members.

In the post on YouTube, Cruz wrote, “I want to be a professional school shooter,” “I have no problem shooting a girl in the chest,” and “I enjoy seeing people die” followed by a smiley face emoji.

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Marjory Stoneman Douglas High School shooter Nikolas Cruz is shown at the defense table during jury selection during the penalty phase of his trial at the Broward County Courthouse in Fort Lauderdale, Florida.

Marjory Stoneman Douglas High School shooter Nikolas Cruz is shown at the defense table during jury selection during the penalty phase of his trial at the Broward County Courthouse in Fort Lauderdale, Florida.
(South Florida Sun-Sentinel via Amy Beth Bennett/AP, Poole, File)

Cruz also sought information on several mass shootings, including at Columbine High School in 1999, Virginia Tech University in 2007, and a black church in South Carolina in 2015.

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Cruz, 23, pleaded guilty in October to 17 counts of first-degree murder. A sentencing hearing will determine whether he is sentenced to death or life in prison without parole.

Marjory Stoneman Douglas High School shooter Nikolas Cruz tucks into his sweater as he waits for potential jurors to enter the courtroom during jury selection during the penalty phase of his trial at the Broward County Courthouse in Fort Lauderdale, Florida.

Marjory Stoneman Douglas High School shooter Nikolas Cruz tucks into his sweater as he waits for potential jurors to enter the courtroom during jury selection during the penalty phase of his trial at the Broward County Courthouse in Fort Lauderdale, Florida.
(South Florida Sun-Sentinel via Amy Beth Bennett/AP, Poole)

The trial in Broward County Circuit Court in Fort Lauderdale went dark Thursday for a pre-scheduled recess and will resume Monday. Prosecutors said they plan to wrap up their case next week by taking jurors on a tour of the building where the fight took place.

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The school has been sealed after the shooting.

The Associated Press contributed to this report.