Florida gunman Nikolas Cruz wanted to be a 'professional school shooter'

Nikolas Cruz is on trial to determine whether he's sentenced to death or life without parole

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Florida gunman Nikolas Cruz wrote online that he wanted to be a "professional school shooter" months before he slaughtered 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 starting seven months before the Feb. 14, 2018, massacre that left 14 students and three staffers dead.

In posts on YouTube, Cruz wrote, "I want to be a professional school shooter," "I have no problem shooting a girl in the chest," and "it makes me happy to see 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 in 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 in the penalty phase of his trial at the Broward County Courthouse in Fort Lauderdale, Florida. (Amy Beth Bennett/South Florida Sun-Sentinel via AP, Pool, File)

Cruz had also searched for 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. The penalty trial will determine whether he is sentenced to death or life without parole. 

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

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

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

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The school has been sealed off since the shooting.

The Associated Press contributed to this report.