SIU says it still hasn't determined how baby died in police shooting near Lindsay, Ont.

Two and a half weeks since a police standoff with a young father that ended with a baby boy dead, the SIU says it is still trying to determine the source of the bullet that killed the infant.

Ontario's Special Investigations Unit said in a news release on Monday that an expert is conducting blood pattern analysis of the inside of a truck driven by the father and the SIU has interviewed 14 police officers who witnessed the shooting.

The SIU collected three police firearms, two rifles and a pistol, as well as pistol from inside a pickup truck at the scene. The pistol from the truck has been submitted to the the Centre of Forensic Sciences (CFS). The SIU said the three police guns will be submitted to the CFS when it is allowed to do so.

Meanwhile, the agency is also awaiting results of post-mortem examinations done on the baby and the father. A post-mortem of the child was done on Nov. 28 and on the father on Dec. 4. 

According to the SIU, the man, 33, and his one-year-old son suffered gunshot wounds in an interaction with Ontario Provincial Police in the City of Kawartha Lakes on Nov. 26. The baby died at the scene. The man died in hospital nearly a week later. Their names have not been released.

"Understandably, there is a pressing public interest in this case, including how the child died and whether it was gunfire from the father or OPP officers that caused the death," the SIU said in the release. 

"The SIU is working to make these determinations. Doing so, however, requires time as key evidence must be examined methodically in line with best practices." 

The agency says an examination of the truck's exterior was completed on Thursday. Blood pattern analysis of the interior is continuing. SIU forensic investigators are documenting, photographing and collecting evidence such as projectiles that they can retrieve without disturbing other evidence, it said in the release.

"Once this step is complete, a trajectory analysis will be performed with the assistance of the CFS in order to aid in understanding the direction of travel of projectiles through the vehicle," the SIU said.

"Following 3D imagery of the truck, the truck will be released to the SIU forensic investigators for another thorough search for evidence. Any relevant evidence obtained will be sent for testing, and in the case of projectiles, will be compared to the firearms collected."

The SIU said it will interview three more police officers who witnessed the shooting on Tuesday. In all, 12 civilian witnesses have been interviewed.

"The SIU assures the public that it is working as expeditiously as possible," the agency added.

The SIU investigates incidents involving police in which death, serious injury, sexual assault or the discharge of a firearm at a person occurs.