The man accused of punching a woman on the subway has been arrested and charged with assault. 

Derek Smith, 56, of Crown Heights allegedly attacked commuter Samantha Saia on the N train Thursday morning. 

Police say the incident began after she complained that Smith was taking up too much space in his seat.

"He punched me and I hit my head against the wall," Saia told News 12. "I was just looking and saw blood on my hands."

It was not immediately clear how Smith was apprehended.