LIVERMORE -- Police are seeking a serial pant-ser, a male culprit who yanks down the pants of lone female joggers then sprints away.
It's a bizarre case that Livermore investigators say has been going on since 2007. Six cases have been reported since then, most in residential areas near Patterson Pass and Mines roads.
The women were not physically injured or sexually assaulted, Livermore police Sgt. Paul Mayer said. Investigators are baffled by who is doing this, and why.
"It's odd," Mayer said. "It's hard to wrap your mind around what he is trying to do."
There appears to be no rhyme or reason for when the man strikes. The incidents have been sporadic -- two in 2007, one in 2008, none in 2009, one in 2010 and two this year. The most recent was April 24, Mayer said.
The incidents have been reported on different days of the week and varying times from morning to early evening.
There's no indication that the man is filming anything. Police wonder if he is trying to satisfy a fetish or practicing for something more sinister.
The incidents do not seem to be related to something called "sharking" which is popular in Japan and Europe. In those cases, men pull down skirts, pants, or tops of women, exposing private parts. These incidents are often videotaped.
Mayer said he hasn't heard the term sharking, but investigators have looked on the Internet to see if the Livermore incidents were taped and posted; they found nothing.
Officials have not found a victim pattern, either. They are different physical types and range in age from 19 to 43. The only thing they have in common is that they each wore sweatpants or shorts. They all wore headphones.
The attacker's description varies, too. Some victims have described him as white, others Latino. In one description, he had a mustache. All the descriptions have him with dark hair. His age ranges from 20s to 40s. He's about 5 feet 8 to about 6 feet tall and weighs 175 to 200 pounds.
"We're not positive it is the same person, but we are treating it like it is," Mayer said.
Dawna Komorosky, associate professor of criminal justice at Cal State East Bay, said she's never heard of anything like what Livermore is dealing with, but says the incident should be taken seriously.
"It is a crime," she said. "The police are right to be concerned about it. I think the women in that area should take precaution."
Runners are heeding that advice.
Livermore resident Lynn Murray said she runs with someone. She worries about the man's intentions and what else he might try on unsuspecting female runners.
"There is kind of a fear factor now," she said.
Even if it is a prank, Komorosky said, it is still an assault and there are ramifications for the victims.
"It is a very fearful experience, regardless of the intention," she said.
The man could possibly face battery, sexual battery, attempted rape or child molestation charges, depending on the circumstances and the age of the victims, Mayer said.
Police and Komorosky suggest running in pairs or groups and varying the route. If listening to music, runners should make sure to be extra aware of their surroundings or keep only one earbud in. Mayer urged runners and joggers to carry a cell phone and, if they know that path veers from street view, to run in the bike lane.
Mayer asks any additional victims to report incidents to the department's dispatch at 925-371-4987. He also asks anyone with information to call him at 925-371-4733.
Contact Sophia Kazmi at 925-847-2122. Follow her at Twitter.com/sophiakazmi.