"From when I've known him, he was one of the nicest people I've known in my entire life," Trieu said.
But after Cruz’s father's death, something changed.
“Eventually after a couple of months, he started talking again, but he couldn't fit back in correctly, and he met the wrong people. They encouraged him and motivated him to do all this wrong stuff, like throw pencils at the teacher and stuff,” Trieu said.
Trieu said as years passed, Cruz became more of an outcast, was bullied, started speaking of violence to the point that in just January, the FBI missed the opportunity to follow up on a warning about Cruz’s gun ownership, desire to kill people, erratic behavior, disturbing social media posts and the potential that he could conduct a school shooting.
Trieu said the last time he saw Cruz was moments after the shooting as students evacuated.
"I remember noticing him walking past us and I remember him blending in wearing a t-shirt that's from the school. He blended in very well and apparently some people greeted him and he greeted back," Trieu said.