Nikolas Cruz already faces the death penalty in the Feb. 14 shooting at Marjory Stoneman Douglas High School.
Zachary Cruz, 18, was driving without a license near a Florida high school. His probation banned him from getting close to schools.
Nikolas Cruz stands to receive an inheritance and annuity from his late mother's estate worth up to $800,000.
Zachary Cruz reportedly told officers he decided to visit Stoneman Douglas High to “reflect on the school shooting and to soak it in.”
Nikolas Cruz, 19, faces dozens of charges for the Valentine's Day attack that left 17 people dead.
Nikolas Cruz faces a maximum sentence of either execution or life in prison.
“Everything everybody seems to know, we didn’t know,” James Snead said of the 19-year-old.