Well the SIU has imposed their mandate here so as far as I know they are the led investigators. They will look into the whole matter.
A warrant was issued by a justice after an information was sworn to under oath. The information set out what grounds the police were relying on to obtain that warrant. It would include what offence it alleges has occurred under the Criminal Code. It could be information from a "know and reliable informant" it could be information obtained through a wire tap. Who knows.... Most often the search warrants are "sealed" in order to protect the identity of an informant or investigative technique. But a search warrant can get "unsealed" if a lawyer can allege his client was set up. This was described as a warrant under the firearms act in one article, so offences were alleged under our firearms laws.