Rosetown Fire Department Chief Dennis Ogg says Wednesday was the saddest day of his life.

"I've been doing this for 41 years and it's tough. You're losing family, what it is."

His fellow firefighter Darrell Morrison was killed in the line of duty when he was struck by a semi-truck while attending the scene of an earlier two-semi crash on Highway 4 just north of Rosetown.

At times Morrison drove him crazy, but his heart was always in the right place, Ogg said.

"Loud, redneck, very opinionated, but a heart of gold. Man, he'd do anything for anybody, that's why he was there.

"I'm going to miss him, you hear the stories but until it happens you don't know what it's like."

Morrison passed his passion for firefighting to his 17-year-old daughter, Cheyanne, who now also volunteers with the fire department.

"I joined in my Grade 11 year because of my dad," she said.

"He was like my best friend, he was my number one fan. He drove me to do everything. He's the reason I want to be a cop, he's the reason I want to go to firefighter college."

She said she can’t believe her father won’t see her graduate high school.

"It feels like he's going to come home."

Morrison’s niece, Jayde, also struggles to wrap her mind around what happened.

"He's probably the best uncle ever, loving fun, someone I've looked up to."

She says she finds comfort in believing her uncle is still looking out for her.

"Even though he already looked out for us down here, now we know we'll have a guardian angel forever.”

Flags were at half-mast around Rosetown on Thursday and a counsellor has been brought in to support families and firefighters suffering from post-traumatic stress disorder.

A GoFundMe me page has been set up to help with costs of the funeral, which is scheduled for next week.

RCMP say it will be two-to-three months before the cause of the incident is determined.