TACOMA, Wash. — Three brothers, two from Wilson High School and one from Giaudrone Middle School, have told police they were involved in last week’s beating of a medically fragile 13-year-old boy on a Pierce Transit bus.

Granted, one of the students denied it at first.

“I didn’t beat the kid,” he allegedly told a police officer this week. “I just stepped over him.”

The boys’ parents are livid about the assault, police say. The parents are working with police, and will discipline their sons. The Giaudrone student will face fourth-degree assault charges.

That’s the good news.

But the beating has revealed troubling gaps in the systems kids depend on to protect them.

The victim, Casey, is a Mason Middle School eighth-grader who does not want his last name used. A week ago, we told you how he was sitting in his usual spot in the handicapped seat in the No. 16 bus at Pierce Transit’s Tacoma Community College transit center on his way to school.

He’s entitled to that seat because he has neurofibromatosis, a disease that causes tumors to attack his nervous system. His spinal cord is deteriorating. One fall could snap it.

It was just after 7 a.m. Sept. 23, and the driver had gone on a break and left the bus doors open, as allowed by Pierce Transit policy.

There was no security officer at the center, said Pierce Transit spokesman Lars Erickson. The agency tracks trouble spots and deploys its patrols accordingly. TCC did not seem to need a patrol.

That morning, a boy got on the bus, pointed at Casey, laughed and left.

Two other boys got on. One hit Casey in the head. Casey rolled under the seat. The boy stomped him.

The other boy took pictures, Casey said. Police have not found pictures or video.

Casey heard laughter from the dozen or so students at the back of the bus.

He heard a woman yell at his attacker to stop. The 45-year-old woman told police the assailant did stop for a moment, and looked at her.

“I will never forget his eyes,” she told Tacoma Police Officer Zachary Smalls, who is stationed at Wilson.

The boy went back to kicking Casey until the woman advanced on the assailant, yelling at him to get off the bus and run. Finally, he did.

When the bus driver returned, all but one of the students in the back of the bus ran away. One young man stayed, apologized to Casey for not helping him earlier and gave his name to police.

When this story ran last week, Wilson Principal Dan Besett and officer Smalls were offended that they did not know about the severity of the attack until they read about it in the paper. Smalls heard it described as a fight off campus. Besett had not heard about it at all.

That’s distressing. The incident involved Wilson kids. Word should travel faster and more clearly, especially to adults in authority positions at the school involved.

Besett also was disturbed that I assumed the kids who ran were from his school. It’s a good community, a safe school, he said. I should write about all the good things Wilson students do.

But the fact is, some of his students ran. They get on the 16 at TCC and get off at Wilson, and have been doing so all school year.

They did not go see Smalls, their school-based officer, to tell him what they saw. They chose not to act in a way to preserve the safety of their Wilson community.

None of their parents have contacted Smalls, which is just as disturbing.

Besett said that if the kids were asked to come forward, they would, but no one had the chance to do that.

“I don’t think the process had a chance to flow,” he said.

I’d like to see that process flow more speedily. The kids saw a beating. They did not intervene. They watched, then ran away. They know the beating was wrong. They know protecting the assailants is wrong. Ten days later, no one has asked them to come forward.

This week, Smalls sent a message to the student, the good citizen, who stayed. By coincidence, one of Casey’s assailants was in the same class and said aloud, “If it’s about the fight on the bus last week, remember, you don’t know anything.”

The teacher heard him, and reported it to Smalls.

By the way, it was never a fight. It was just a brutal attack on a sick boy cowering under a bus seat.

One more fine Wilson student arrived after the attack. She stayed to comfort Casey, who was bleeding from his nose and mouth. She spoke with police.

When she got to school, after doing the right thing, she was marked tardy, her father told me. Punished.

Smalls said he will look into that.

Last Saturday, after he read the paper on his day off, Smalls came to work and started his investigation.

Later, he interviewed the witnesses and got identifications using a yearbook photo montage. Detectives met with the alleged attackers and their parents.

“It has been difficult sorting who did what, but we have a good case,” said Smalls.

Casey’s father met with Det. Mark Hardeman, who said the brothers and Casey had exchanged words.

A few weeks ago, Casey said, he joked with some of the kids at the back of the bus, went back to his seat and forgot about it.

The brothers told detectives Casey talked smack to them, and they started plotting how to make him pay.

After the beating, the family contacted Pierce Transit repeatedly, but got no return call until Wednesday. That person told them they had to take down the reward posters they had put up at the transit center.

Pierce Transit administrators met with the family Friday, apologized and offered to pay Casey’s medical bills. They are examining policies to better protect riders.

They were already preparing to install cameras on all buses. It is the system’s only capital improvement this year.

Meeting with the family was a fair, if somewhat slow, response from one of the agencies involved.

The others would do well to evaluate how they dealt with the beating of a frail kid.

There’s no real safety in a community that tolerates an incident like this.