A 25-year-old Gidgegannup cyclist killed when he was hit by a truck early yesterday has been remembered as a tireless volunteer who always put others first.

Kaleb Smith was cycling to work along Toodyay Road when he was clipped by a Hino 500 truck near the intersection of Reen Road about 5.15am.

The collision flung Mr Smith off his bike and into a gravel ditch. Passers-by quickly came to his aid and desperately tried to revive him.

The truck driver also rushed to the young man's side and watched on in horror as attempts to bring him back to life were unsuccessful.

Police arrived at the scene soon after and took over CPR attempts until St John Ambulance arrived.

Mr Smith's wife Lauren received a worrying phone call a short time later from workmates at Subway in Mundaring who said he had not arrived at work.

He was an assistant manager at the store where he had worked for the past seven years.

Mrs Smith is understood to have heard a radio news report about the crash and was visibly distressed when she arrived at the scene of her husband's death.

The area where Mr Smith died is a 100km/h zone and has a gravel shoulder with no bike path.

He was wearing dark clothing and a dark helmet but he did have a back and front light on at the time of the crash.

The couple had recently celebrated their third wedding anniversary.

Mr Smith was heavily involved in his local church, Eastgate Church in Mt Helena, and yesterday afternoon the church's pastor, Jared Kealley, released a statement about the 25-year-old. He said his church and community were in shock.

"Kaleb was a warm, loving, caring young man, who always put others first," he said.

"He volunteered a lot of his time caring for the young people in our community running youth programs, and engaging them through music."

Major crash investigators are asking for anyone who saw the crash or helped with Mr Smith's resuscitation attempt to contact Crime Stoppers on 1800 333 000.