The dead bird was recovered from the Wyrley & Essington Canal near The Lea in the Blakenall area of Walsall by an RSPCA team after reports that people were seen stoning a family of swans.
Residents took to social media to complain after suspects walking two dogs in the vicinity were allegedly seen using a catapult to hit the birds.
A woman, who did not want to be named, for fear of reprisals said: "I think it's disgusting. What pleasure do people get out of attacking a family of swans and stoning them?
"People should not be doing that. It's not funny and swans are protected wildlife. Those responsible have no respect for life whether wildlife or otherwise. Where does it stop? Today it's swans, tomorrow horses then it escalates. Killing seems to be the way of the world these days.
"These swans were attacked near The Lea field at about 6pm on Saturday. One of the swans was killed and the RSPCA was called after one of the birds was seen floating in the water.
"People in the area are worried about speaking up for fear of repercussions. There is talk that the two people who had two dogs with them were responsible and the male who used the catapult to hit the swan was an adult."
The woman added that the Blakenall councillors had also been informed of the incident.
In a statement the RSPCA said: “This shocking and intentional act of cruelty will have caused this swan significant pain and suffering before death.
“We share our space with wildlife and need to show respect and kindness. Animals feel pain, just as we do. It’s disgusting to think that anyone could take pleasure from firing a catapult at a living creature."
The charity warned that taking, injuring or killing wild birds, or to damages their nests and eggs, is illegal and can lead to a six-month jail term and an unlimited fine.
Anyone with information should contact the RSCPA on its appeal line, 0300 123 8018.