WHITE RIVER, Ont.—Passengers who witnessed a man viciously attack a 20-year-old fellow passenger on a Greyhound bus bound for Winnipeg over the weekend are demanding to know why police put the alleged attacker on the bus in the first place.

Anita Daher, a Winnipeg author sitting behind the driver when the attack occurred, said she watched police put David Roberts on the bus in Wawa, Ont., on Sunday afternoon as it travelled west between Toronto and Winnipeg.

Shortly after, she heard a commotion from the back of the bus and saw a man clutching his chest in pain.

As Daher dialled 911, she said Roberts demanded to be let off the bus before the next scheduled stop near White River, roughly halfway between Thunder Bay and Sault Ste. Marie. Police arrested him a short time later on the side of the Trans-Canada Highway.

Roberts, from Manitouwadge, about 400 kilometres east of Thunder Bay, was charged with aggravated assault and two counts of breach of probation. He is scheduled to appear for a bail hearing Tuesday morning.

It’s unthinkable that another attack could have occurred after the gruesome beheading of a young carnival worker on a Greyhound in Manitoba this summer, Daher said.

It’s also not clear why police would have put him on the bus in the first place, she added.

“I certainly want to know how this happened,” Daher said in an interview shortly after finally returning to Winnipeg on Monday afternoon. “I would certainly like to see some security measures put in place. We want to see Greyhound take action.”

Provincial police say they were “assisting” local officers with the alleged attacker shortly before he boarded the bus.

But Ontario provincial police Const. James Searle said he couldn’t comment further since it occurred within the jurisdiction of local police.

“We’re still looking to see if we can determine . . . a little bit more in terms of the actual chronology of the events,” Searle said. “That investigative procedure is still ongoing.”

Calls to the Wawa police service weren’t returned but CBC News reported local police arrested Roberts for causing a disturbance earlier on Sunday and released him.

Roberts reportedly requested psychological help and was taken to hospital by police where he was deemed not to be a threat, CBC said. Police then purchased him a bus ticket when he asked to go home, which the force says is common practice.

The victim and his attacker don’t appear to have known each other so police are still trying to determine what motivated the attack, Searle said.

The 20-year-old victim, who has not been identified, was taken to hospital in Wawa and later transferred to Sault Ste. Marie.

The man’s injuries were not serious and he’s expected to be released from hospital shortly, Searle said. Although Daher said it wasn’t clear whether the young victim had a deep wound or a shallow one, Searle would not confirm the victim had been stabbed.

“Until that full investigation is completed, it’s down as an assault at this time but he is charged with aggravated assault,” Searle said.

Floyd Sabourin, a Pic Mobert First Nation resident who was riding the bus at the time of the incident, said he had been dozing near the alleged victim when he heard voices yelling about “someone having a knife.”

It wasn’t clear if the victim had been stabbed, “but he was bleeding, anyway,” Sabourin told a Thunder Bay newspaper. “It was pretty loud.”

The incident hasn’t soured him on taking the bus but Sabourin said something must be done to prevent future attacks.

The latest attack comes as Greyhound continues reviewing bus security — a taxpayer-funded “risk-assessment” which has been going on for more than a year-and-a-half.

Greyhound spokeswoman Abby Wambaugh wouldn’t comment on the ongoing police investigation but said the bus company got a grant from Transport Canada to review the risks posed to passengers riding on bus lines like Greyhound.

The assessment looks at current security measures and whether changes need to be made, she said. But Wambaugh said she didn’t know when the assessment might be finished.

“Once that’s complete, we will work with (Transport Canada) and talk with them about our recommendations and discuss what — if any — security measures makes sense to be implemented for inner-city bus transportation,” Wambaugh said from Dallas.

Transport Canada wouldn’t comment on the incident.

There were 14 passengers on board Sunday’s bus to Winnipeg. Daher said she deliberately sat at the front because McLean had been stabbed at the back of the Greyhound on which he had been riding.

After letting off the accused, the driver continued to White River, where an ambulance rushed the victim to hospital. The remaining passengers were questioned by police and then put back on a Reid Bus Line charter en route to Thunder Bay before heading to their final destination.