A Brooklyn man was riding the subway in the middle of the day when he heard a woman belt out a blood-curdling scream. When it carried on for longer than a few seconds, he looked in her direction then immediately went barreling through the cowards who were watching.

When the doors to the No. 3 train opened at the Bergen Avenue stop in Park Slope, Maurice Osborne, 37, said he heard screams from a woman, who investigators said was being sexually assaulted in the middle of the day. “Usually when you’re on the train, you hear commotion.