Tim McLean, shown in a photo taken from his MySpace page, was heading home to Winnipeg when he became the victim of a horrific slaying on a bus.

Some passengers who witnessed Tim McLean's horrific death on a Greyhound bus last summer are still having problems coping with their memories.

McLean, 22, was stabbed to death and beheaded on July 30, 2008, while he was on his way home to Winnipeg from Edmonton.

His attacker, Vince Li, was found not criminally responsible because of his mental illness and is receiving treatment for schizophrenia in a Manitoba psychiatric hospital where he will remain until doctors say he's no longer a threat to society.

If Li ever recovers, he could one day be released without a criminal record. That worries Kayli Shaw, 22, a passenger who saw the attack and has been diagnosed with post-traumatic stress disorder.

"I understand some doctors may think schizophrenia can be cured and they may think that Mr. Li can be cured too and be sane, but some medications can be changed, [even] discontinued. A person can say they're taking their medications when they're not," she said.

"So, they may think he's sane but I still wouldn't feel any easier if he was on the streets."

'Everyone's been hurt by this and everyone on that bus will not be who they once were. They're all changed and, none of them, it was not their fault.'—Stephen Allison, bus passenger

Shaw was moving from Alberta to Ontario to escape the abuse of her past, be closer to her new boyfriend and start a new life. But her new life has not been what she expected.

"Before, there was so much hope. I wanted to get a job, be able to support myself, prove that I could be independent, be OK being so far away from my family," she said. "Now, I'm so dependent. I have so many bad days that I don't even want to get out of bed."

Shaw got on the bus in Edmonton and settled in as it lumbered through Saskatchewan and into Manitoba. After a stop in Brandon, Man., she began watching a Zorro movie. Just after 8:30 p.m., as the sun was starting to set, she heard screaming and realized it wasn't from the movie.

"I took off my earplugs and looked back behind me and [saw] the attack going on. I was able to hear Tim McLean scream," she said. "It still haunts me till this day, the scream, and seeing what was going on. I remember the bus driver pulling over and telling us all to get off the bus as fast as we could."

Shaw and 33 other passengers, as well as RCMP officers, watched as Li paced inside the bus and held up McLean's head.

"When I saw Mr. Li holding Tim's head I thought, 'What's the purpose? Why aren't the police shooting him? Why aren't they trying to get hold of him? Why don't they do something — hop on the bus, do something, anything.'"

Li was arrested five hours later, after he jumped out a bus window. His lawyers never disputed that he killed McLean but convinced a judge in March that he was not criminally responsible because of an untreated mental illness.

Vince Weiguang Li leaves provincial court in Portage la Prairie, Man., in August 2008. (Rob Swystun/Portage la Prairie Daily Graphic/Canadian Press)

He was hearing voices he believed were from God, telling him to destroy the demon sitting beside him, or he would be killed himself, a psychiatrist testified at Li's trial.

"Ever since that night, I have nightmares of seeing myself standing at the same spot that I was, I remember seeing the bus, I still hear Tim McLean's screams," Shaw said. "I can't even go out at night by myself or with my boyfriend. It triggers that I'm back in that spot having to see the beheading all over again.

"I have so many bad days that I don't even want to get out of bed."

She isn't the only one. Other passengers say they are on medication for depression and stress.

Some are having problems working or studying. Many, like Stephen Allison, are still asking why Greyhound hasn't provided more counselling or compensation.

Allison and his wife were sitting across the aisle from Li when he attacked McLean.

"It's been very difficult for us and we didn't even do anything wrong. We were in the wrong place at the wrong time and someone should be there to help us — something to say, 'We're sorry for your loss,' because everyone's been hurt by this and everyone on that bus will not be who they once were," he said.

"They're all changed and, none of them, it was not their fault."

Counselling available: Greyhound

Stuart Kendrick, senior vice-president for Greyhound Canada, told CBC News the company has offered financial help and counselling for passengers on a case-by-case basis. It's still available for anyone who needs it, he said.

Greyhound has also done a lot to improve safety on its buses, he added.

'It's hard to relive every day and no amount of medication will put it away or drown it out.'—Kayli Shaw, bus passenger

"We did introduce some of the passenger screenings at our major terminals, as well as on-road policies on what items can be carried on board. We maintain that we are one of the safest modes of travel," he said.

The McLean family has launched a civil suit against Greyhound, Li and the Canadian government. The family's lawyer, Jay Prober, believes Greyhound could be doing much more to increase passenger safety.

"Why only some locations [for screenings], why not all locations? If a bus driver is properly trained, all he needs is a portable metal detector so he can screen people who come into the bus. That's one little step," he said.

"It's clear that Greyhound failed to protect their passengers when they allow people to carry weapons on the buses. The main challenge [in the lawsuit] will be to try and persuade the defendants to do the right thing and settle the case so they don't have to relive the details of this horrible tragedy."

But passengers like Shaw may relive the horror of that night for the rest of their lives.

"It doesn't feel like a year. It seems like yesterday," she said. "Counselling helps, but it only goes so far. So it's hard to relive every day and no amount of medication will put it away or drown it out."