A screen capture of video released by police shows a suspect in two robberies of spas in Cambridge and Watertown.

Cambridge police are investigating an armed robbery at a massage and spa business in North Cambridge at around 5:50 p.m. May 14 – which they and Watertown police believe was followed with another spa robbery in that neighboring community two days later.

The spa has a staffed front desk where the robber stopped to demand money. He yelled “Give me the cash” while pointing and jabbing a silver knife of 6 to 12 inches in the direction of the worker there, according to a police report. “This made her very afraid,” according to the report by officer Miguel Mijares-Munoz.

Another worker, monitoring security cameras in the basement, dashed upstairs to confront the robber, who by that time was outside the residential-style business, on the sidewalk. When confronted, the man pulled out the knife again and brandished it, causing the worker to jump back, skinning his knee and forearm, the report said.

The robber was described by workers as being around 28 to 34 years old, standing perhaps 5-foot-9 with a thin build. They thought he may have been a light-skinned black man with an accent – perhaps Haitian, according to a couple of the primarily Mandarin-speaking workers. The robber wore a black jacket, black cap and mask, and possibly gloves.

A driver on Norris Street heading toward Massachusetts Avenue saw the confrontation on the sidewalk with the knife and circled the block, hoping to see which direction the robber ran – which was down Norris Street toward Cedar Street, then south toward Middlesex Street, police said.

Two days later, a spa in Watertown was robbed in the late afternoon by the same person, police believe.

Armed robbers more frequently target banks and minimarts, “but if cash is provided for tips or services at businesses, that may have been a factor” for targeting spas, said Jeremy Warnick, director of communications and media relations for Cambridge police.

Anyone with information about the Monday incident is asked to call (617) 349-3300 or make contact anonymously. If the robber is encountered, the public is asked to not try to interact with him and call 911 as soon as it is safe.