Any person who knowingly causes, procures, aids, counsels or creates by means of fire or explosion a substantial risk of serious physical harm to any person or damage to any building the property of that person or another, whether or not used for residential purposes, which is occupied or in use for any purpose or which has been occupied or in use for any purpose during the six (6) months preceding the offense or to any other residential structure, shall, upon conviction, be sentenced to imprisonment for not less than five (5) years and may be imprisoned for life, or shall be fined not less than three thousand dollars ($3,000) nor more than twenty-five thousand dollars ($25,000), or both; provided, further, that whenever a death occurs to a person as a direct result of the fire or explosion or to a person who is directly involved in fighting the fire or explosion, imprisonment shall be for not less than twenty (20) years. In all such cases, the justice may only impose a sentence less than the minimum if he or she finds that substantial and compelling circumstances exist which justify imposition of the alternative sentence. That finding may be based upon the character and background of the defendant, the cooperation of the defendant with law enforcement authorities, the nature and circumstances of the offense, and/or the nature and quality of the evidence presented at trial. If a sentence which is less than imprisonment for the minimum term is imposed, the trial justice shall set forth on the record the circumstances which he or she found as justification for imposition of the lesser sentence.