Grandmother dies after being punched in the face by a 23-year-old. Her grieving brother says he has ‘no earthly idea why’ it happened.

A 23-year-old man has been charged with manslaughter after fatally punching an elderly woman in the face last month in New Orleans, leaving the victim's family questioning what motivated the brutal attack.

"We have no earthly idea why this happened," Jeffrey Johnson, brother of 61-year-old Margaret "Jane" Street, told the New Orleans Advocate on Wednesday. "It won't bring my sister back, but it helps knowing who did it and that they have him."

The New Orleans Police Department reported Tuesday that Jeremiah Mark struck Street with a closed fist in the city's French Quarter on April 19, causing her to fall to the ground and hit her head on the concrete. Street suffered a traumatic brain injury from the attack and later died at the hospital.

The two were reportedly engaged in some kind of argument when the crime was committed, the Advocate noted, though the outlet said details about the dispute were not provided in a sworn police statement filed in court.

The incident was originally classified as a simple battery, but following Street's death and an autopsy, authorities changed the classification to a homicide.

After positively identifying a suspect, authorities released a photo of him to the public, prompting Mark to come forward about his involvement in the altercation. Mark turned himself in to police on April 22, reportedly confirming to police that "he used his hand to push [Street] in the face."

He has been charged with manslaughter and, if convicted, could serve up to 40 years in prison.

Street's family held a funeral for her on Thursday in her hometown of Decatur, Alabama. Her obituary noted that she retired from a job at General Motors and is survived by a daughter and two grandchildren.

Johnson, Street's brother, told the Advocate that he fears his sister's death was the result of a robbery gone wrong.

"It just seems like she was at the wrong place at the wrong time," he said.