This is asinine and comparable to suing a hammer maker because you smashed your thumb. Even if someone smashed someone elses thumb, on purpose. It is not the fault of the tool maker. It is the responsibility of each person to handle those tools appropriately. Decisions come with consequences. Use a tool for harm, and that person should deal with those consequences, not a company who made it.
Firearms dealers should only be dealt with legally if they sold someone a gun without going through the proper process.