Investigators found that a tear gas device thrown by a New Mexico sheriff’s deputy likely caused the house fire that killed 15-year-old Brett Rosenau in early July. Rosenau had run into the house with an older man whom Albuquerque authorities were pursuing for allegedly violating his parole on charges of armed carjacking and stealing cars. The incident turned into a standoff, and the Bernalillo County sheriff’s deputy threw a tri-chamber canister designed to produce an irritating gas into the house to smoke out the pair. Instead, investigators said, the device landed on a mattress, which then caught fire, killing Rosenau from smoke inhalation, according to an autopsy. The Albuquerque Police Department said the device “cannot be eliminated” as the fire starter. While fire officials have ruled the blaze as accidental, they said all other potential sources for the fire have been ruled out based on their investigation.