FORT LAUDERDALE, Fla. — The man accused of gunning down 17 people at a Florida high school registered to vote while behind bars awaiting trial.

The SunSentinel reports Nikolas Cruz registered as a Republican on July 25. He’s charged with 17 counts of first-degree murder and 17 counts of attempted murder for the Valentine’s Day massacre at Marjory Stoneman Douglas High School in Parkland.

Andrew Pollack, the father of a victim, tweeted Saturday that he’s “sick to his stomach” Cruz was allowed to register in jail and criticized Broward Sheriff Scott Israel for allowing it. But Cruz hasn’t been convicted of a crime and was eligible to vote this year.

Sheriff’s spokeswoman Veda Coleman-Wright says the supervisor of elections controls the process. Once inmates are registered, absentee ballots are mailed to them in jail.