He was stunned by the hit but managed to get back to his feet with assistance, then left the pitch and walked unaided to the changing rooms, accompanied by a doctor.
There, he lost consciousness numerous times and when emergency services arrived around 8pm (local time), he passed away, according to the report.
It is understood he wanted he to return to the field, but he then began to vomit.
"We will find out why he died and if the tackle provoked his death," the local prosecutor's office told La Montagne.
The prosecutor said when Fajfrowski "left the pitch his condition did not appear to be alarming. He even wanted to return (to play) afterwards, but he then began to vomit."
Magne, a pivotal figure in France's Rugby World Cup semifinal win over the All Blacks in 1999, is Aurillac's most famous former player.
He told RMC, a French radio station, that he was shattered at Fajfrowski's death.
"It's a whole club, a city, a department and all the French rugby that are affected, who are bereaved, it's a family member who went away, it's very sad for French rugby.
"It is necessary to wait for the autopsy, do not draw an early conclusion.
"But there is an evolution [in] professional sports in general. We are going towards more speed, intensity, violence, there are more and more difficult contacts and they could be avoided.
"We will have to quickly provide answers."
Magne said rugby must move towards "less violent" tackles.
He said more tackles were being launched "on the upper body with the shoulder at the level of the head".
"That causes a lot of KO [knockouts]."
