CHICAGO (CBS) — A woman was groped by a stranger while riding her bicycle with her husband.

CBS 2’s Dana Kozlov reports the incident happened on Milwaukee Avenue, one of the most popular bike routes in the city. At almost any hour, especially during the day, dozens of cyclists can be seen on the path.

On Saturday, a husband and wife were assaulted while riding their bikes along the route. The culprit was riding a small motorcycle.

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The victim says it began at the busy intersection of Milwaukee and Augusta shortly after 4 p.m. Saturday. The 33-year-old woman says she and her 35-year-old husband were waiting to turn left on their bikes when a man on a green motorcycle drove by and groped her from behind.

The woman says he was with another man on another small motorcycle, who sped off first.

Security video from a nearby building shows him leaving. The suspect, riding a green motorcycle seen in the upper right corner of the security video, followed a few seconds later, trailed by the woman’s husband who gave chase. She followed behind.

At Milwaukee and Division, the situation escalated. The woman’s husband confronted the suspect, who then punched him, knocking him unconscious and to the ground, before speeding off.

Witnesses took photos of the attacker, forwarding them to the victims who say they want him caught.

The couple said they are rattled by the incident, but are okay. The woman says her husband was punched with some sort of

Chicago Police are investigating.