"He was playing music, making jokes while he's doing it, had slogans and rhymes he kept saying," student Trenton Beazely said of the suspect on "Good Morning America." "Every time he'd kill someone he'd say, 'another one bites the dust.'"
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Sources tell ABC News that 17-year-old Dimitrios Pagourtzis allegedly incorporated aspects of previous mass shootings for the shooting at Santa Fe High School that took the lives of eight students and two substitute teachers.
Pagourtzis apparently wore a black trench coat, like the gunmen in the Columbine shooting.
Santa Fe, a town of 13,000, came together Sunday for prayer services at local churches and the traditional end-of-school baccalaureate service. Mourners also gathered at a Houston-area mosque to remember the life of a slain exchange student from Pakistan.
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Pagourtzis has been jailed on capital murder charges.
A statewide moment of silence was observed Monday morning to recognize those killed and wounded in the shooting.
ABC News contributed to this report.