The Brooklyn District Attorney's Office says no criminal charges are expected at this time in Thursday's shooting on an A train in Boerum Hill.

The shooting left a 36-year-old man in critical condition and had landed another man in police custody.

"Yesterday's shooting inside a crowded subway car was shocking and deeply upsetting," said a spokesperson for the Brooklyn District Attorney's Office. "The investigation into this tragic incident is ongoing but, at this stage, evidence of self-defense precludes us from filing any criminal charges against the shooter."

Police say a 36-year-old man boarded a train at Nostrand Avenue and evaded his fare. Upon boarding, they say he began provoking a 32-year-old man on the northbound A train around 4:45 p.m.

Police say the 36-year-old took out a sharp object and began menacing the man. At some point, officers say a woman intervened and injured the 36-year-old aggressor with a sharp object.

Authorities say the 36-year-old man took out a gun but that the 32-year-old grabbed the gun and shot the 36-year-old multiple times, striking him in the head. The 36-year-old man is currently in critical condition.

Police say multiple officers were on patrol at the Hoyt Street station as the train pulled in. They responded when the gunfire was heard.

Police had also been seeking the woman connected to the incident.