Six women have been targeted so far.
Police say some of the victims have had to go to the hospital. One person was struck in the face. Another woman who was targeted was visibly pregnant.
Photos released by Waukegan police show some of the injuries sustained by the female victims, the BBs or pellets piercing the skin.
"We do believe them to be very serious injuries, and the potential for extraordinary injuries is very apparent," said Sgt. Cory Kelly, Waukegan Police Dept.
Police say at least half a dozen incidents have been reported in various parts of Waukegan. And though investigators won't say where they've occurred, all the victims were struck near intersections while on foot.
The news was alarming to the many out for a stroll Tuesday.
"It's just scary. All we're trying to do is get a little exercise done and enjoy the nice weather out in the sun," said Jami Imroth, Waukegan resident.
Investigators say all but one of the victims was female, and the one man who was hit was with a group of women.
"That just is not OK, to be shot and pregnant? I don't care, shot by anything is just not OK," said Chi O'Neal, Waukegan resident.
"Obviously ruthless. I mean, this is not a joke. I don't know what kind of reaction they're trying to find, but physically harming someone like that, it's a huge concern," said Lauren Miscenic, who works In Waukegan.
BB and pellet guns are remarkably lifelike. At first glance, it's hard to tell a BB gun from the real handgun that shoots bullets. The metal BBs and pellets, as well as the guns, can be purchased at many big-box or sporting goods stores.
"I hope they catch him because I don't want it to be any one of my female relatives or friends, loved ones, none of that. I hope they catch him," said Harrison Colburn, Waukegan resident.
"If this were to happen to somebody, we ask that they immediately call 911, ascertain if they need medical assistance, and we want to get police officers in the area as soon as possible to try to catch the offender," Kelly said.
Police do not have a description of the offender or offenders. At two of the shooting incidents, a white vehicle was spotted driving away, but police don't have a make or model.
Additional information can be found at the Waukegan Police Facebook Page.