[cincinnati65]

Speaking to the BBC, Commander Tim Juris said he was was on the fourth floor of the building when he heard shots.

"It sounded like a tap gun as opposed to a real gun," he said.

http://www.independent.co.uk/news/world/americas/us-navy-yard-shooting-at-least-four-killed-in-gun-attack-at-washington-military-site-8819771.html

[Lazamataz]

Dafuq is a tap gun?

[Springfield Reformer]

What is a tap gun?