'All we know for sure is a domestic situation obviously got out of hand and we have a deceased subject as a result,' said Lt. Tim Diamond with the West Bloomfield Police Department.
The grandmother's attorney claimed that Hoffman was on drugs and that his client was not responsible for her actions, saying: 'She didn’t have a choice - she was afraid.'
Jerome Sabbota said the teenager had been in trouble for using drugs, and added: 'She’s taking care of somebody else’s child... and he was on probation for drug issues.'
He continued: 'I don’t think she was in control of her emotions. She was afraid. She’s not a big, strong woman.'
But Jonathan's father, the suspect's former son-in-law, was sceptical of her explanation, saying: 'I don’t have the intimate details of his involvement with drugs.
'I just don’t see how that fact, if it is a fact, would have any justification for what happened.'
Officers were called to the residence, which the 17-year-old shared with his grandparents, at about 5.30pm after neighbours heard gunshots, according to the Detroit Free Press.
The grandmother was taken into custody but not immediately questioned. Because of her age and the circumstances of the shooting, the woman is being guarded at a local hospital.
Hoffman, a senior at Farmington Central High School had been out with friends at the movies the night before he was shot according to Freep
'He was one of the funniest kids I know,' said Adam Makhoul, 17, of Birmingham, one of the friends who saw The Dictator with Hoffman the night before he died.
'He was never violent. He always was a giving person.'
And police have revealed that Hoffman had been living with both his grandparents at Maple Place Villas when the fatal shooting occurred.
'He’s a kid that didn’t deserve to die,' said Max Dashevsky, 17, of West Bloomfield, who knew Hoffman since ninth grade.
'I woke up this morning thinking I was going to see this kid, that it was just a dream.'
The boy had called 911 about 40 minutes before he was pronounced dead, Lt. Diamond said.
Officers seized a handgun that they believed was used in the slaying before escorting the old woman from the property.
'She’s a really nice woman. I hope the best for her,' neighbor, Elizabeth Ardisana, 85, told the newspaper.
The teen's grandfather was not present when the shooting took place.
The boy's parents, who are divorced, have moved to Arizona with his 15-year-old daughter, but Jonathan stayed in Michigan to complete his education.
Officers responded to similar domestic violence involving the teen and his grandmother in March, at the same address.
Lt. Diamond said the March incident was 'a verbal argument'.
'Officers resolved it. It was your typical teenager-parent argument,' he said.
The March police report did not specify whether the grandmother or the teenager instigated the dispute, the newspaper said.
Lt. Diamond said investigators expected to get a search warrant this weekend so they could 'go over this residence with a fine-tooth comb' for evidence.
The elderly woman will be brought to West Bloomfield police station for questioning when she is able to leave hospital. She will be held in the lockup.
Prosecutors will review the case next week for possible criminal charges.