Metro is asking the public for help tracking down a man who robbed a woman of her purse Wednesday morning on a Metrobus.

A black man wearing a denim jacket and black hoodie showed the woman his gun and demanded her purse, Metro officials said. The robbery happened around 8:54 a.m. on the W6 bus near the intersection of Stanton Road and Elvans Road Southeast.

The robbery comes as serious crimes on Metrobuses climbed in 2012, with an average of 11 per month, versus seven per month in 2011. Three people were killed on Metrobuses in 2012, The Washington Examiner previously reported.

Metro released a photo of Wednesday's robber. Anyone with information is asked to call Metro transit police at 202-962-2121.