Pete Davidson revealed the devastating way he found out his dad was killed on 9/11

Pete Davidson was just seven years old when his dad died in the World Trade Centre on 9/11.

It's been 24 years since the world watched in horror over the 9/11 tragedy.

The terrorist attacks, the deadliest to ever happen on American soil, saw Islamist extremists Al-Qaeda hijack two planes to crash into the Lower Manhattan buildings while a third aimed for the Pentagon.

A fourth, which was planned to hit Washington D.C., then crashed into a field in Pennsylvania after passengers and crew fought back. As for the Twin Towers, both the North and South skyscrapers erupted into flames and collapsed.

The devastation claimed the lives of almost 3,000 people, with one of those being Davidson's father, Scott.

Now, the Saturday Night Live star has opened up about the traumatic moment he lost his father on that fateful day, September 11, 2001.

Pete lost his father when he was just seven (Steve Granitz/FilmMagic)

His dad, who was a firefighter, was last seen charging into the Marriott World Trade Center, just moments before the structure collapsed.

Speaking on the Real Ones with Jon Bernthal podcast last year, Pete said he was just seven years old when his father told him he was 'going to pick [him] up' that day, but never did.

"I got picked up by my mom. She didn't tell me what was going on for like three days. She kept telling me dad's at work, I had no idea. My mom's like, 'You're just grounded, you're not allowed to watch TV'," he said.

"I was like, 'What? I didn't do anything.' And then one night I turn on the TV and I saw my dad on TV."

Pete said it was here that he learnt about his father's death as the TV presenter had announced the death of all the firefighters, though it was touch and go for some time as the family were unsure if Scott was dead or alive amid hefty search and rescue missions.

Scott Davidson died during the 9/11 terrorist attacks (National Fallen Firefighters Foundation)

"There was just some sort of hope, and it was just up and down and nobody knew the right way to deal with it," he added.

The 31-year-old admitted he now struggles with PTSD after his father's death and has had extensive therapy throughout his life, as well as trust issues.

"Dad says he's going to pick you up, he doesn't, so for life I don't believe anyone," the comedian said. "I'm trying to learn how to believe people, and Hollywood isn't the best place to learn that skill. I went from traumatic life to high school traumatic life, because Hollywood's like high school."

However, he says he keeps his father's 'memory alive' by sharing 'little jokes here and then about him', adding: "My dad was a great dude."

He also shared admiration for his mom for what she went through, being only 30 years old at the time.

"That's why, as I get older, I'm like, 'Man, my mom was awesome," Pete said.