GAITHERSBURG, Md. (CBSDC) — A 21-year-old woman was sexually assaulted near a lake in Green Farm Conservation Park at about 5:05 p.m. Monday afternoon, according to Montgomery County Police.

She told investigators that a man approached her from behind with a knife, assaulted her, then fled toward Bernish Drive.

View mugshots of local criminals

The suspect is described as Hispanic, between 5 feet 5 inches and 5 feet 7 inches tall, weighing 150 to 160 pounds. He was wearing jeans, a white t-shirt and a black knit cap.

Green Farm Conservation Park has a Gaithersburg address but is considered part of the Hadley Farms community, an area between Gaithersburg and Laytonsville.

Both police and neighbors said a sexual assault is all but unheard of here.

“Extremely, extremely rare,” Montgomery County Lieutenant Jacques Croom said Monday night. “Great community. Crime rates here are extremely low. This is something we’re taking a hard look at.”

Resident Anita Jones came by the Hadley Farms community pool with some neighbors at the sight of police cars and news trucks. She says the woods’ seclusion holds the potential for danger.

“Not this kind of thing though.” Jones said. “This is shocking, really shocking.”

Anyone with information about this sexual assault is asked to contact the Homicide/Sex Section at 240-773-5070. Those who wish to remain anonymous may contact Crime Solvers of Montgomery County toll-free at 1-866-411-TIPS (8477) or 240-773-TIPS (8477) or submit a tip online. Crime Solvers is offering a cash reward of up to $1,000 for information provided to them that leads to an arrest in this case. Anonymous tips can also be provided by typing “MCPD” plus the tip on a cell phone or PDA and texting it to 274637 (CRIMES).