According to Ugandan television station NTV, Massa was shot at by police in a road incident.
Massa is said to have hit a police motorcycle before speeding off which forced police to retaliate.
The report further suggests that a woman who was a passenger in the car driven by the well-travelled forward died on the scene after the alleged confrontation with the police.
Massa is recovering at Gwatiro Clinic in Bweyogerere.
He announced his retirement from international football after leading Uganda at the Africa Cup of Nations finals in Gabon in January.
The 31-year has also turned out for Al-Masry, El-Shams, Jomo Cosmos, Itesalat, Yenicami Agdelen and University of Pretoria.