BART police are investigating an altercation on a 16th Street train where one person was injured, police said.
At approximately 7:30 p.m. and altercation began on board and continued on its way to the Civic Center Station where the suspect fled.
A BART spokesperson described the altercation as physical and said a weapon was involved.
The victim sustained injuries and was transported to the hospital and their condition is unknown.
A person of interest is in police custody.