Maya, 59, is the father of Zakhele Maya, the community leader who helped organise last year's service-delivery protests in Siyathemba township in Balfour, Mpumalanga.
Following the protests the police stormed into the Maya home, looking for Zakhele. When they didn't find him, they turned to his father and allegedly assaulted him with the butt of a pistol.
Maya is now suing Police Minister Nathi Mthethwa for R20-million in damages.
A report from psychologists from the Centre for the Study of Violence and Reconciliation said: "On assessment, Mr Maya presented with severe symptoms of post-traumatic stress disorder. It seems his assumptions of the world as a benevolent and meaningful place have been shattered by this incident."
The report stated that Maya said he suffered from extreme nightmares, intrusive memories of the incident, irritability, angry outbursts, feeling jumpy, startled responses, sleeping difficulties, hopelessness and helplessness.
Maya, who attended five counselling sessions, said his situation was exacerbated by the Independent Complaints Directorate ICD - the police watchdog body tasked with probing crimes committed by police - which he said was "dragging its feet in finalising the investigation".
"It's been more than a year. Every time we call them [the ICD] we are told the investigating officer is in a meeting. I need an update ... It's sad that they are not updating us."
Zakhele Maya, who helped organise the violent protests in which a library was torched and shops looted, said it has become clear to the family that the investigation will never see the light of day. "We are now approaching the second year. If you pick up the phone tomorrow, they will tell you they are investigating. What is it that they are investigating? There is no justice," he said.
"Justice favours those with power. If you are poor, as we are, there is no justice."
As a result of getting no joy from the ICD, Maya said he was now considering to ask the Public Protector Thuli Madonsela to probe the violation of his father's rights.
ICD spokesman Moses Dlamini could not be reached for comment.
Maya's lawyer, Dominic Thinane, also could not be reached for comment.