Prosecutor Jim Flaiz, upon learning Ohio school shooter T.J. Lane was going to make a statement in court Tuesday, told relatives of his victims to be prepared for something inflammatory.

Lane's own lawyer told the court he urged his client not to make the type of statement that the attorney expected to be delivered.

But no one could have fully foreseen the actions and words of Lane, who entered the courtroom and removed his blue button-down shirt while the judge and those in attendance took their seats.

Lane, now 18, revealed a white T-shirt with the word "killer" written on it.

The attire was similar to what he was wearing when arrested by police shortly after the February 27, 2012, killings at Chardon High School in northeastern Ohio.

Given the opportunity to speak a few minutes later, Lane made an obscene gesture at the victims' families and spoke to them briefly, using explicit language.

"What he did was beyond anything I could envision seeing in a courtroom," Flaiz told CNN a few hours after a judge ordered Lane to spend the rest of his life in prison without parole. "I was shocked and disgusted at how the defendant conducted himself."

Lane smiled and smirked during much of the hearing, laughing when Flaiz described him as an "evil person."

According to the Geauga County prosecutor, Common Pleas Judge David L. Fuhry was unaware that Lane had the lettered T-shirt. "I think everyone felt the effect of that shirt at the same time," said defense attorney Ian Friedman, according to CNN Cleveland affiliate WJW. Friedman said he, too, had no advance knowledge of the T-shirt.

Lane pleaded guilty last month to three counts of aggravated murder, two counts of attempted aggravated murder and weapons-related charges.

The death penalty was off the table because of Lane's age at the time of the crimes, according to prosecutors.

For their part, victims' relatives kept calm and made their own statements, describing the pain they felt and the profound loss to both themselves and the community. They also cited the contributions of their killed or wounded loved ones.

"I was very proud of the family members in the courtroom," said Flaiz, adding he was not sure he could have kept his composure if he were in their shoes.

The mother of a wounded student now confined to a wheelchair looked directly at Lane as she told him he was fortunate so many officers were in the small courtroom.

"Because of you, our town will never be same," Holly Walczak said. "Why? Why did you do it? Why?"

Walczak said she has watched her son, Nick, suffer daily in the year since he was shot in the school cafeteria and in the hallway when he was pursued by Lane.

"You are evil. I will have to eventually forgive, otherwise you will haunt me," she told Lane.

Demetrius Hewlin, 16, died from his wounds.

His brother, Philip Carter, read a statement in court on behalf of mother Phyllis Ferguson.

"In our humanity, we still cannot understand why his life was taken in such a violent manner," said Carter.