Ontario’s police watchdog says three officers who fired their guns during a standoff that killed a baby still haven’t made themselves available to be interviewed by investigators.

“The three subject officers, who were designated as such on the basis of information that they each discharged their firearm in the course of the incident, have not as yet availed themselves of an opportunity to be interviewed,” the Special Investigations Unit (SIU) said in a news release on Friday.

The unit noted that “subject officers” are not under any legal obligation to speak to the SIU but are allowed to do so.

SIU investigators have interviewed 18 witness officers and 14 civilian witnesses so far about the incident on Nov. 26, in which a man, 33, and his one-year-old son suffered gunshot wounds in an interaction with Ontario Provincial Police in the City of Kawartha Lakes.

The baby boy died at the scene. His young father died nearly a week later in hospital. 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.

“The SIU is working to make these determinations. In so doing, it is imperative that best investigative practices be strictly adhered to, including the sequencing of various forensic examinations in the proper order.”

The SIU said four firearms — two rifles and a pistol belonging to the police, as well as a handgun from inside a pickup truck at the scene — have been submitted to the Centre of Forensic Sciences (CFS), along with a number of spent cartridge cases. The guns are being examined, the SIU said.

An expert has conducted blood pattern analysis of the inside of a truck driven by the father and the CFS has completed its analysis of the truck. The vehicle has been released to the SIU, which is searching it for further evidence.

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.

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