A man knocked a woman out with a glass bottle at the Williamsburg bar Union Pool in an unprovoked attack late last month, according to the NYPD.

Police are searching for the unidentified man, who ran off afterwards.

Investigators say the 22-year-old woman was standing inside the bar shortly before 3 a.m. on February 23rd when the man walked up to her from behind and hit her in the head with a glass bottle, according to a release from the NYPD.

She fell down and passed out, and emergency responders took her to New York Presbyterian Hospital, police said. She suffered a concussion, pain, and bruising.

Police said it is not known why she was attacked. An eight-second video released by the NYPD shows the man standing with a group of people, seemingly in an argument.

Anyone with information in regard to these incidents is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782). The public can also submit their tips by logging onto the CrimeStoppers website, or on Twitter.