LOVELAND, Colo. — The overnight killing of a man on a sidewalk has raised fears that a serial shooter might be trolling roads in northern Colorado after a bicyclist was recently gunned down and a driver was wounded.

Police and the FBI have refused to comment on the possibility of a serial shooter. But they have offered a $10,000 reward for information on the first two unsolved shootings that authorities say are related — though they haven’t said how.

The bicyclist was found dead May 18 along a rural road in Windsor, and the motorist was driving on Interstate 25 on April 22 when she was shot in the neck and survived. Officials say it’s too early to know if the sidewalk shooting late Wednesday in Loveland was connected to those attacks.

All three shootings occurred within 15 miles of each other.

“We don’t have any specific information from the shooting that occurred here last night that this case is related,” Loveland Police Chief Luke Hecker said.

However, he noted that there are enough similarities to investigate a possible link.

In the latest case, 65-year-old William Connole was found on a sidewalk along a main street, and responders were unable to save his life. Family and neighbors say Connole had survived cancer and often took late-night walks through his quiet neighborhood.

Sadie Rogers, 15, said Connole was her grandfather and had worked for years in the computer industry before taking a job at Home Depot. She said the nighttime walks helped him sleep after work.