Driving to Canada on a family trip, City Councilman Kenyatta Johnson couldn't believe what he heard.
His nephew told him about instructions available online that teach viewers how to print out a gun.
"At first I didn't take him seriously," Johnson said Thursday.
But when he came home from vacation, he hopped on YouTube, "And saw several different disturbing video clips that show how individuals can create a gun using a 3-D printer."
Johnson proposed a bill on Sept. 12, which passed City Council on Thursday, that bans the use of three-dimensional, or 3-D, printing technology to manufacture firearms. 3-D printers build objects with layers of plastic that hardens into familiar shapes.
The state regulates the ownership, possession, transfer or transportation of guns and ammunition, but not the manufacture of firearms for personal use, Johnson said.
Shira Goodman, executive director of CeaseFirePA, said she thinks the bill sends a message.
"I think it sends a message to the people of Philadelphia that we care about the city and that they want to take steps to protect it," Goodman said, "And I think it sends a message to Harrisburg that if you're not going do it, we are."
Goodman said she's not sure if the bill will be tested by the state and possibly sent to court as has happened in the past with previous ordinances.
Johnson, founder of the anti-violence organization Peace Not Guns, said Philadelphia is one of the first cities "to proactively address an issue that has the potential to pose a significant danger to the public,” he said.
“As technology progresses, three-dimensional printers will become more advanced, less expensive, and more commonplace," he added. "As instructions for the manufacture of guns via 3-D printing technology are already available on the Internet, we could be looking at a recipe for disaster.”