The merciless ring of the wall-mounted telephone forced Arnold Roma out of the kind of heavy sleep that only his 12-hour hospital shifts could lull him into. He’d only been home from work for five hours, anyway.

Squinting against the morning sunlight threatening to consume his Staten Island living room, the then-49-year-old pulled the corded phone to his ear and, before he could even open his mouth to say hello, was greeted by piercing sirens on the other end.

“A plane just hit the World Trade Center!” a voice bellowed. It was his son, Keith, yelling into the receiver over the horns and chugging engine of a firetruck.

The father – a nurse, volunteer firefighter and retired NYPD officer – stiffened for an instant as fond memories of running calls with his son and riding on the truck at the New Jersey fire company they volunteered at together flashed in his mind.

He was awake now.