Cruz, through his attorneys, had previously expressed a willingness to plead guilty to avoid the death penalty.
In its filing, the prosecution said that, among the aggravating factors spurring its decision, were that Cruz knowingly created a risk of death for many people, his crime was aimed at hindering "any government function or the enforcement of laws" and that the shooting was "especially heinous, atrocious or cruel".
Broward County Public Defender Howard Finkelstein originally offered for Cruz to give a guilty plea in exchange for a life in prison sentence.
Prosecutors announced Tuesday they will be seeking the death penalty in the case. "We are not saying he is not guilty but we can't plead guilty while death is still on the table", Mr Finkelstein said.
Counter-terror police investigate 'unexplained' death
There is no evidence to suggest a link to the March 4 poisoning of former spy Sergei Skripal and his daughter, the statement said. The death of a 68-year-old Russian man in London is being investigated by counter-terrorism officers, Scotland Yard has said .
The Parkland massacre has sparked a wave of student activism, renewed political tension over gun control and even forced the normally pro-firearm friendly Florida Legislature to pass a law tightening access to the weapons. After surgeries, his condition was upgraded to fair, his attorney and the hospital said.
Meanwhile, a student who is credited with saving the lives of 20 students by attempting to close and lock a classroom door during the attack is improving at a hospital.
Borges' family has filed notice that they will sue Florida authorities to seek money to cover the cost of his recovery.
The defendant was arrested shortly after the shooting at the high school, which is the worst high school shooting in USA history.