Police are asking for help in tracking down a suspect who punched a woman in the face and then stole her purse on the Lower East Side Tuesday. He followed the woman, who is in her mid-20’s, into a building at 50 Allen St (between Grand and Hester), at around 4:20 in the afternoon. The suspect, caught on surveillance video, is thought to be in his mid-30’s. He was wearing a white shirt, jeans and white shows. If you have any info about this crime, contact Crime Stoppers at 800-577-TIPS.