IOWA CITY - Recent attacks have police in Iowa City puzzled. Since September of last year, police have received 24 reports of assaults on young women. The latest was early Sunday morning.

Now, college students at the University of Iowa are definitely on edge.

Allyson Bone says, "I'm an art student, and sometimes I don't get off work until 1 a.m. or 2 a.m., and I'm not going to walk home because of what I've heard."

In 23 of the 24 incidents, the woman was alone and was sometimes distracted, often on a cell phone. Each incident is similar. The victim is approached from behind and the suspect sticks his hand up her skirt. In some cases, he pushes her to the ground. The women then scream or fight back and the suspect leaves.

Sgt. Troy Kelsay with the Iowa City Police Department says, "The people that this is happening to, it's going to be a long time before they feel safe walking alone, they're traumatized."

In response to these attacks, police have done things like change patrol patterns and they continue to investigate yet they haven't been able to identify a suspect. That's why they're going back through incident reports looking for something they might have missed.

Sgt. Kelsay adds, "I'm hoping we can narrow down an area or a time, maybe even some evidence, a witness statement or video from some place nearby. I don't know, I'm just hoping to find something that was missed before."

Now, for the first time, Crime Stoppers is offering a reward of up to $1,000 for any information that leads to an arrest.

Until that happens, college students say they're not taking any chances.

Lindsay Ricker says, "I usually get a ride or take a taxi but if it's dark, I won't walk by myself."

Police add, they believe one man is responsible for many or most of these attacks and he won't stop unless he's caught.

The attacker in the most recent assault is described as a white man in his 20s, 5’ 4” tall with dark hair that's possibly shaved. This description is consistent with similar attacks.