His office was on the 61st floor of the south tower of the World Trade Center, and during a break, he looked out the window and shuddered.
The north tower was ablaze, but he didn't know why.
"Luckily, our manager said, 'Don't take the elevators,' " said Danni, who began making his way down the stairs with thousands of others.
"I got down to the 55th floor and that's when the second plane hit the tower 20 floors above me. Being from California, it felt like an earthquake. The building shook, the walls cracked."
At about the 30th floor, Danni said, he passed firefighters headed up the stairwell while he was headed down, and he presumes some or all of them later died trying to save lives. Danni made it out safely, then outran the dust cloud that surged through lower Manhattan when the towers disintegrated.
This past Monday, Danni heard the news about Boston while at work in Glendale and was reminded once more of our vulnerability and the preciousness of life. He checked in with his wife.
"I've got two small kids now," said Danni, "and I squeezed them a little tighter" Monday night.
When they are older, he will tell them they have to be careful and at times vigilant.
"But I also will tell my kids they have to live their lives."