Mother left him $800,000 and he was going after his share.
Two months before the Florida school shootings, Nikolas Cruz hired an attorney in an attempt to get his portion of an inheritance left to him and his brother from his mother, according to Fox News in "Nikolas Cruz tried to access $800,000 inheritance before shooting: report."
The woman who took Cruz in after his mother's death, is also attempting to get permission from the court to administer the estate. She is on friendly terms with Cruz's brother, although reports suggest that Cruz believes she is trying to steal his inheritance.
Much of this money could get eaten up in legal fees. However, there might be some left over to help the victims of Cruz's crimes. It will be up to their estates to make claims. In this situation, the most likely way they will go about doing that, is by intervening in the estate of Cruz's mother. This could prevent Cruz from using the money to pay any bills he has in the criminal case against him.
Reference: Fox News (Feb. 26, 2018) "Nikolas Cruz tried to access $800,000 inheritance before shooting: report."