Rohnert Park police Monday were still searching for a motorcyclist who rode away Sunday after crashing into and seriously injuring a bicyclist.

The motorcyclist was riding a black, older-model motorcycle with saddle bags at 1:24 p.m. Sunday when he or she struck the bicyclist, a 68-year-old Windsor man, Sgt. Aaron Johnson said.

The motorcyclist was heading south on Redwood Drive near Willis Avenue near the In-N-Out Burger restaurant.

The exact circumstances of the crash remained unclear Monday, and police had not determined who was at fault.

The bicyclist apparently was heading toward the Fresh Choice parking lot across the street, Johnson said.

"All we know is that the motorcycle hit the rear of the bicycle," he said. "We don't know which direction the bicycle was going."

The bicyclist was in stable condition Monday at Santa Rosa Memorial Hospital after suffering moderate-to-major injuries, including a fractured pelvis, abrasions and contusions, Johnson said.

He declined to identify the man, saying he needed to interview the victim and didn't want anyone else talking to him.

The motorcycle appeared to be a Honda or Suzuki model from the 1980s or 1990s.

Anyone with information about the crash can call 584-2600 and ask for Johnson or Officer Ryan Foiles with the Rohnert Park Department of Public Safety's traffic bureau.

You can reach Staff WriterJulie Johnson at 521-5220, or on Twitter @jjpressdem.