The dog that witnesses say attacked a man in central Hamilton Wednesday night did not cause his death directly, said the regional coroner, and it is unclear what role the dog played in the incident.

"There's no credible evidence that a dog attack is material in the death process," said Regional Coroner Jack Stanborough after a post-mortem examination Thursday. "We don't know what role the dog played."

So what did happen? It may be months before further tests can reconcile the medical findings with the dramatic witness accounts of a vicious attack.

Stanborough told CBC News additional testing, including toxicology and microscopy, will be done to determine the exact cause and manner of the death, adding that it might take weeks, if not months, to get the results back.

Hamilton police said the incident happened at 11:15 p.m. ET when two men were walking a dog along Burton Street, in central Hamilton.

"The dog began to attack one of the men and he collapsed," according to a police news release. "A passerby intervened and using a baseball bat, attempted to fend off the dog."

The man was pronounced dead at the scene.

The mauling of the man in his thirties led to desperate efforts by others to try to pull the dog off the screaming victim.

Witnesses recall apparent attack

Earl Secord said the man's screams brought him outside.

"I've never heard anybody scream like that before," he said.

After witnessing the apparent attack, he went back inside his home to grab a baseball bat to join a group of people trying to fend off the dog, which was attacking the man's torso and neck areas, Secord said.

"It just looked like, for whatever reason, he was gonna take out that guy and that was it," Secord said. "And there was no stopping."

Secord added that the dog wasn't attacking anyone else and seemed to be focused on the man on the ground.

Secord said he has witnessed dog attacks before, but this incident has been a particularly heavy one.

"Nobody wants to see somebody get ripped apart by a dog," he said. "I never knew a dog could do that and just keep going."

Victim 'hurt bad'

Another neighbour, Bert Stoner, said he called 911 just after 11 p.m. ET.

"I went outside — that's when I see the guy on the ground with the dog on top of him."

Stoner said he saw two or three people trying to get the dog, which he described as "fair-sized," off the man.

"He was hurt bad," Stoner told CBC News.

Several witnesses said they saw police point their guns at the animal but did not fire any shots.

There is a disconnect between the witnesses' reports and the coroner's investigation, said Stanborough. However, it is not unusual for the witnesses to take things out of context during a fast-paced, traumatic event, he added.

"It's a lot more difficult to gain perspective," he said.

Further investigation

The city's animal control department now has possession of the dog, police said.

Hamilton police spokesman Const. Steve Welton said it is unclear if the dog belongs to the people walking him. Police will be working with animal services to determine who the owner is, he said.

Residents initially described the dog as a pit bull, but city spokeswoman Ann Lamanes said municipal animal control officials have confirmed it is a Sharpei Fila mix and weighs about 20 kilograms.

The dog will likely be put down because of the "nature of the incident," said Lamanes. Officials are now checking to see if the dog was licensed and trying to find its adoption history.

Fire crews were called to the scene as well, but were called off before they had any contact with the man.

"We had the information that it was a dog bite," said fire department spokesperson Claudio Mostacci, adding that they were told the man had no vital signs.