The first sound — a muffled pop — caused little alarm. It had come from somewhere on the third floor of a home in East Williamsburg, Brooklyn, shared by musicians from Iran.

The men had been unwinding with a routine video game of Internet pool, each comfortably ensconced in his own room, lazily playing before bed. The next sound came from one of the men, Arash Farazmand, who wondered aloud, “What’s that?”

Two more blasts, now well inside the home, had the unmistakable thunder of weaponry. And then there was the sound of someone dying.

It was soon clear that a gunman was methodically moving through the house.

“He was stepping so fast,” Pooya Hosseini recalled on Thursday, describing the deadly scene that unfolded just after midnight on Monday inside 318 Maujer Street and his confrontation with the gunman — a fellow Iranian musician — that enabled him to survive.