From Guns.com:

“This is a piece of metal that you can easily buy in the markets,” said Bridgeport Police Chief AJ Perez in a press conference, holding up an unfinished 80-percent AR lower. “But if you can get this, you can make this,” he said, holding an AR-15 short-barreled rifle. “And this is a real weapon. This weapon will discharge anywhere from 50 to 30 rounds at a time.”