CHICAGO (CBS) — One gun has now been tied to four different shootings, including two tragic murders in Rogers Park that terrorized the city last fall.

The first shooting happened on a sunny day 10 months ago when a man was shot and killed while walking his dogs. That gun has never been recovered, but it’s left a trail of destruction behind for months.

Flowers marked the spot on the sidewalk where 73-year-old Douglas Watts was inexplicably shot once in the head at close range last September.

Within 36 hours, the killer struck again. This time it was 24-year-old Eliyahu Moscowitz, who was also shot point blank, just a few blocks away in Loyola Park.

The men didn’t know each other, and nothing was taken from either of them. But police said they were shot with the same .40 caliber gun and released surveillance videos of a person of interest. They show a slim man with a hat and scarf covering most of his face, who ran with a distinctive gait.

To this day, both murders have gone unsolved.

But we now know the gun that took both their lives didn’t go into retirement. It showed up again 15 days later on the West Side, in the 4300 block of West Fifth Avenue, where it was used to shoot two men who were stopped at a red light when a dark-colored SUV pulled up alongside them and someone inside opened fire.

Five months later and about three miles away, the gun made its most recent appearance in the 2300 block of West Jackson Boulevard. The security guards at a residential building reported that a white vehicle drove up the driveway, then backed out and someone started firing shots. Fortunately, no one was hit.

Right now, police can’t say for certain if the gun ever changed hands, but a study released last month by the University of Chicago Crime Lab shows gun swaps are common.

Of the 221 people convicted of gun-involved offenses surveyed, a majority acquired their primary gun “through a purchase or trade” and “from a friend or acquaintance.”

Chicago police say they’re continuing to ask the community for information that might help solve any of the crimes.

The reward for information about the Rogers Park killer is now at $150,000.

Megan Hickey