CENTENNIAL, Colo. — The mother of Colorado theater shooter James Holmes gave an impromptu public apology Tuesday, telling a judge during his sentencing hearing that her son feels remorse but his mental illness and medications made it hard for him to express it.

Arlene Holmes took the stand after more than 100 victims and survivors of the 2012 attack testified about the searing physical and emotional scars the shooting has left.

“We cannot feel the depths of your pain. We can only listen. ... And we pray for you,” she said through tears. “We are very sorry this tragedy happened and sorry everyone has suffered so much.”

Standing at a lectern with her husband, Robert, by her side, she told Judge Carlos Samour Jr. that she has been researching mental illness and ways to prevent mass violence.

Samour today will formally sentence James Holmes to life in prison without parole and up to 3,318 additional years on attempted murder convictions. Jurors convicted him of murdering 12 people.