An unhinged man pummeled a mother and son in an unprovoked attack on a Brooklyn train last week, cops said. 

The 55-year-old woman was on a 2 train with her 21-year-old son at the Franklin Avenue station in Crown Heights just after 8 a.m. Jan. 10 when the suspect suddenly hit her multiple times on the head and body, authorities said.

Then he turned his attention to the woman’s son, striking him repeatedly as well, police said. 

The suspect took off after the assault. Cops released a photo late Monday of him inside Atlantic Terminal after the incident. 

Both mother and son refused medical attention for swelling and bruising, cops said.