A year and a half on from that rainy Sunday morning, his grief is still raw.
"I can't speak for anybody else in my family about what it's like, but there are moments when you think of him and it just triggers it off. It's a long process."
The Otago University student first met Mr Gregory, nicknamed "Red", three years before he married his sister Sarah in 2008.
The pair shared a love of soccer and as a college student Mr Bitchener would often be roped into his brother-in-law's Saturday morning Army team.
"He was such a nice guy, laid back, and fitted in very well with our family - we are quite a sporting family and he was great fun," he said.
"He was mad into soccer, but then he was into most sports and would give everything a crack."
Mr Bitchener instantly thought of him when he had the Phoenix squad sign a special fan's t-shirt at a pre-season match in Dunedin last month.
The shirt has been listed on Trade Me to benefit The Missing Wingman's Trust, founded by Flight Lieutenant Tim Costley last year after his fellow pilot Nick Cree died in an air accident.
Mr Gregory's father and trust member, Steve Gregory, was moved by the gesture.
"It just came out of the blue," he said.
"We had no idea he had planned it, and he just said, I've got this thing I'd like to do and what do you think? It was a really nice gesture and very, very genuine."
Mr Gregory said Cameron had been especially "badly cut up" by the tragedy.
"Cameron and Dan were very close family and a lot of that was forged on the football fields and cricket pitches where they shared a lot of good times. I'm really pleased that Cameron has found a way to support our charity and honour my son at the same time.
"I really hope people get behind this auction because they'll get a really unique shirt in what we hope will be a memorable season for the Phoenix, but they'll also be supporting the families of our RNZAF service personnel and that's something they can take a special pride in."
Show your support
* Log on to Trade Me and place a bid on the auction titled "Wgtn Phoenix Special Southern Fever Signed T-Shirt".
* Donate funds or your services to the The Missing Wingman's Trust by visiting www.missingwingmantrust.org.nz