COLORADO SPRINGS, Colo. -

Colorado Springs police are investigating a report of a sexual assault just a few blocks from the Sand Creek police substation near Academy and Fountain boulevards.

A woman told police she was walking in Prairie Grass Park around 9 p.m. Friday when a man grabbed her, took her to a nearby vehicle and then sexually assaulted her.

The man was possibly wearing a dark mask, police said.  The assailant fled and remains at large.

It's the second sexual assault in two weeks at a park. On Aug. 16, police said a woman was attacked at gunpoint around 10:30 p.m. at Village Green Park near Academy Boulevard and North Carefree Circle.

The victim said her assailant first confronted her in a parking lot at the Greentree Village Apartments.  That assailant also escaped and hasn't been found.

Diane Paulsen, a certified karate instructor who also teaches basic self-defense skills to women, said the victims were at a disadvantage by being alone at night.

"Use your hands and look a threat in the eye to let him know you're not to be messed with," she said.  "If he persists, punch or kick in vulnerable areas and scream.  Believe it or not, that will discourage most threats."

Paulsen said self-defense tactics don't guarantee that a victim won't be harmed, but it will make her less likely to become a victim.

"I have about 10 women in my monthly classes," she said.  "For a city of this size, there should be more interest in self-defense.  My classes should have 30 or more women in them."