The Special Investigations Unit (SIU) says OPP were called to a home on Belsyde Avenue East in Fergus for reports of a domestic disturbance around 11 a.m. on Sunday.
"There was an interaction with the OPP officers and the man, he was armed with two knives," said Kristy Denette, a spokesperson for the SIU. "The OPP discharged a conductive energy weapon followed by a firearm and the man was pronounced dead at the scene."
An OPP officer was taken to hospital with serious injuries.
Mathias's family said he was struggling with mental health issues, adding they were planning to have an intervention with him this week to get him help.
"Today we were supposed to take him to have him put on a 72-hour hold in hopes to get more help for him for mental health," said Rachel Labrie, Mathias's sister. "Instead I watched my brother being carried out in a body bag."