CENTENNIAL, Colo. (AP) — There was plenty of horror in the courtroom as Aurora police officers gave detailed accounts of the grim scene after a gunman killed 12 and wounded dozens others during a July rampage at a packed movie theater.

What was missing Monday was an explanation as to why James Holmes, 25, might have launched the attack. That’s what drew dozens of survivors and reporters to the first day of what is expected to be a weeklong hearing to determine whether Holmes will stand trial for the shooting.

“I mean, basically my son came out here to go to school. He never came back. He came back in a jar. So I would at least like to know what happened,” said Tom Teves, of Phoenix, whose 24-year-old son Alex was killed in the attack. “There’s no way to understand this because there’s no understanding it, but we want to know at least what happened.”