A MAN who lost his gay son to suicide and was walking across America to raise awareness about bullying is dead after being hit by a truck in Colorado.

The Colorado State Patrol says 48-year-old Joseph Bell died after being struck along a two-lane highway in a rural area northwest of Kit Carson. Investigators believe the driver fell asleep.

Bell's 15-year-old son, Jadin, died in February after hanging himself in a schoolyard. He had reported being bullied, but he didn't leave a suicide note.

Bell began his walk in April and planned to finish on the Delaware coast.

The truck driver, 49-year-old Kenneth Raven, has been charged with careless driving resulting in death.