A man found dead on a sidewalk late Wednesday raised fears in northern Colorado that there could be a serial shooter in the loose after a bicyclist was recently gunned down and another driver was wounded.

Police and the FBI refuse to comment on the possibility of a serial shooter, but have offered a $10,000 reward for information about the first two unsolved shootings, which they claim are linked.

The bicyclist was found dead May 18 along a rural road in Windsor. The motorist was driving on Interstate 25 on April 22 when she was shot in the neck and survived. Officials say it is still too early to determine whether the sidewalk shooting in Loveland was connected.

All three of the shootings have 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, a cancer survivor, 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.

Even when he had cancer, Connole would come to her softball games, Rogers said.

"He just did everything for everyone he could," she said.

Neighbor Russell Harmon said it seems like the shootings could be linked.

"I've got two children and a wife, and I don't want to be outside playing with my kids, you know, they're riding bikes or something down the sidewalk and somebody (could) come by and shoot me or them," he said.

Detectives are consulting with members of a task force as they continue to investigate whether the attacks are linked, police say.

FBI special agent in charge Thomas Ravenelle said it would be inappropriate to comment on whether the shootings were the work of a sniper.

Windsor police Lt. Rick Klimek said tips were pouring in about the cyclist shooting but so far none have provided substantial leads. The tips have involved years-old shootings, suspicious vehicles and other information. Investigators check each one.

"They're all going into a database to see what, if anything, fits together," Klimek said. "People are just hypersensitive now to their surroundings."

Drivers in northern Colorado have reported a string of broken vehicle windows since the I-25 shooting. However, investigators have not confirmed whether gunshots were involved in those cases.

If the cases are the work of a serial shooter, he or she likely has no connection to the victims or any particular target, said Eric Hickey, dean of the California School of Forensic Studies who has studied serial killers.

The victims are "proxies for his anger and whatever he's angry about," he said, speaking generally.

"He'll make mistakes," Hickey said "They always do."

The Associated Press contributed to this report.