It happened shortly after 4:30 p.m. Wednesday.
Police say an off-duty Delaware State Trooper was jogging on South Park Drive when she ran up on a man touching himself inappropriately under a pavillion.
She confronted him and he took off. The off-duty trooper called police.
Police were able to collect DNA evidence at the pavilion that could help identify the man.
Authorities are looking for a white or Hispanic man, 25-29 years old. He was wearing a black T-shirt, black shorts and bright blue New Balance sneakers.
Police say it is the second incident of this kind in less than two weeks on South Park Drive.
In that case, a woman was jogging in park just before 7:00 p.m. on September 15th when she says a man ran past her exposing himself.
The suspect in both cases the suspect is described as a white male in his mid-20s to 30s with a thin build. He was wearing bright blue sneakers.
Police think the man could be a runner who knows his way around the park.
They've increased patrols hoping to keep this person from trying to do this again.
Anyone with information about the case is asked to call the Wilmington Police Confidential Tip Line at 302-576-3990, Crime Stoppers at 1-800-TIP-3333 or submit tips online at www.tipsubmit.com.