Gents, I am not a lawyer, nor do I play one on TV. That stated, this is the section of Michigan Firearms Law that may apply to charging the parents.
Remember, Michigan is not Texas. Oxford in in Oakland County, the rich suburb area Northwest of Detroit.
The question is did the parents "allow any firearm under his immediate control" to kill another person.
From a simple Google search:
FIREARMS LAWS OF MICHIGAN Page 155 CARELESS, RECKLESS, OR NEGLIGENT USE OF FIREARMS Act 45 of 1952 AN ACT to prohibit the careless, reckless or negligent use of firearms and to provide penalties for the violation of this act; and to repeal certain acts and parts of acts. History: 1952, Act 45, Eff. Sept. 18, 1952. The People of the State of Michigan enact: 752.861 Careless, reckless or negligent use of firearms; penalty.
Sec. 1. Any person who, because of carelessness, recklessness or negligence, but not wilfully or wantonly, shall cause or allow any firearm under his immediate control, to be discharged so as to kill or injure another person, shall be guilty of a misdemeanor, punishable by imprisonment in the state prison for not more than 2 years, or by a fine of not more than $2,000.00, or by imprisonment in the county jail for not more than 1 year, in the discretion of the court. History: 1952, Act 45, Eff. Sept. 18, 1952. 752.862 Careless, reckless or negligent use of firearms; injury of property; penalty.
Sec. 2. Any person who, because of carelessness, recklessness or negligence, but not wilfully or wantonly, shall cause or allow any firearm under his control to be discharged so as to destroy or injure the property of another, real or personal, shall be guilty of a misdemeanor, punishable by imprisonment in the county jail for not more than 90 days or by a fine of not more than $100.00, if the injury to such property shall not exceed the sum of $50.00, but in the event that such injury shall exceed the sum of $50.00, then said offense shall be punishable by imprisonment in the county jail for not more than 1 year or by a fine not exceeding $500.00. History: 1952, Act 45, Eff. Sept. 18, 1952. 752.863 Section repealed.
Sec. 3. Section 235a of Act No. 328 of the Public Acts of 1931, being section 750.235a of the Compiled Laws of 1948, is hereby repealed. History: 1952, Act 45, Eff. Sept. 18, 1952. 752.863a Reckless, wanton use or negligent discharge of firearm; penalty. Sec. 3. Any person who shall recklessly or heedlessly or wilfully or wantonly use, carry, handle or discharge any firearm without due caution and circumspection for the rights, safety or property of others shall be guilty of a misdemeanor. History: Add. 1955, Act 14, Eff. Oct. 14, 1955. Compiler’s note: Section 3, as added by Act 14 of 1955, was compiled as MCL 752.863[a] to distinguish it from another section 3, deriving from Act 45 of 1952 and pertaining to the repeal of MCL 750.235a. The compilation number formerly assigned to this section was MCL 752.a863. 752.864 Firearms; injury to person or property, suspension of hunting privileges.
Sec. 4. In addition to the penalties provided in other sections of this act, the court may suspend the hunting privileges of any person convicted of violating any provision of this act for a period of not to exceed 3 years from the date of conviction.