The man is described as Hispanic, possibly in his 30s and 5 feet 6 inches to 5 feet 7 inches tall. He was last seen wearing a black jacket, black gloves, a black knit hat and black pants.
Police have also released a photo of a vehicle similar to the one seen leaving the area at the time of the incident. They believe the man got into a teal- or mint green-colored Dodge Neon or similar type of car, with a spoiler attached to the trunk. Another person was driving the vehicle.
The U.S. Postal Service is offering up to $25,000 for information leading to an arrest and conviction of the person responsible for the crime.
The 31-year-old female letter carrier was stabbed in the abdomen while on the job Monday afternoon. She is expected to make a full recovery, city officials reported.
Rockville City Police Chief Terrance N. Treschuk said the incident occurred at approximately 2:45 p.m. at the intersection of Halpine Road and Alsace Lane while the mail carrier was on her delivery route.
The woman was sitting in her mail truck when a man approached her and showed a knife, city officials said. The man said in Spanish that he was going to rob the woman, the city reported.
The woman grabbed for the knife and was stabbed, officials said.
The postal employee was taken to Suburban Hospital in Bethesda, Treschuk said. She was listed in stable condition, city officials reported Wednesday.
Her name was not released because she is a witness to the crime.
Luvenia Huyson, a spokeswoman for the U.S. Postal Service in Maryland, said late Monday afternoon that postal officials had no statement about the incident. She said the letter carrier worked at the main post office in Rockville, located at 500 N. Washington St.
U.S. Postal Service inspectors are investigating whether anything was stolen from her mailbag or mail truck.
The Rockville City Police Department's Criminal Investigation Unit, U.S. postal inspectors and Montgomery County Police are investigating the incident.
Police are asking anyone who might have seen the man or witnessed the incident to call 240-314-8938.
To contact the U.S. Postal Inspection Service, call 877-876-2455.