A criminal investigation has been launched into the emergency medical care provided to a Good Samaritan who police have said was killed after trying to intervene in an altercation earlier this month in Hamilton, Ont.

Yosif Al-Hasnawi -- described by police as a brave young man who was trying to do the right thing -- was shot and killed on Dec. 2 after he tried to help an older man who was being accosted by two other men.

The men have since been charged in connection to the death.

But witnesses to the interaction have criticized Hamilton paramedics and police for not taking Al-Hasnawi seriously when he said he was in pain.

Earlier this month, Tom Raczynski, who lives in the area, said he heard screams that drew him out of his home that night.

"He was lying there complaining he was hurting and they kept saying he was faking," Raczynski said of paramedics and police at the scene.

"The one paramedic kept saying 'oh you're a good actor,"' Raczynski said. "I just thought it was disgusting. Like somebody's shot, you take him in to the hospital, you don't leave him lying there."

Hamilton police say the Niagara Regional Police Service will conduct the investigation to ensure the investigation is impartial.

"It's about time," Raczynski said when he heard about the criminal investigation.

Raczynski said Niagara police have yet to contact him, but Hamilton police brought him down to the station for a statement about the paramedics' behaviour about a week and a half ago.

Russell Crocker, deputy chief of the Hamilton Paramedic Service, said two days after the 19-year-old died that the service launched an investigation into the incident as a result of information it received.

Hamilton police didn't say whether its officers were under investigation, and said it wouldn't provide any further comment while the investigation is ongoing.

But in a written statement, spokesman Const. Jerome Stewart wrote that the force believes a criminal investigation is warranted based on a review of the preliminary evidence.

Neither Niagara police nor Hamilton paramedics immediately responded to requests for comment.