(CNN) -- A Delaware pediatrician has been indicted on 471 felony counts in the alleged sexual abuse of his patients, prosecutors announced Monday.

The Sussex County grand jury indictment accuses Dr. Earl Bradley, 56, who has had a practice in Lewes, Delaware, for more than 10 years, of victimizing 103 children -- all but one girls. The charges range from rape and sexual exploitation of a child to endangering child welfare and assault.

Delaware Attorney General Beau Biden told CNN Radio the indictment is based on "video and digital evidence" seized from Bradley's home and medical practice in December. Authorities have not ruled out additional charges, he added.

"The reality is that as a prosecutor, the rules prohibit me from telling you exactly how I feel -- and I'm feeling a great deal today," Biden said.

Bradley also has medical licenses in Pennsylvania, New Jersey and Florida. Authorities have said they have contacted officials in those states.

He was initially arrested and charged in December.

Bradley's attorney, Eugene Maurer Jr., said he would base his client's defense on mental health.

"Most of the evidence in this case comes from videotapes -- it's kind of hard to argue with videotapes," Maurer said, adding, "The issue in this case is going to come down to his mental health at the time."

Biden said Bradley will be arraigned within four to six weeks.