Hundreds of mourners crowded into an Alberta church Wednesday for the funeral of a young woman killed by her ex-boyfriend on an Alberta highway after a night out celebrating a birthday with friends.

More than 850 people gathered at the Evangelical Free Church to remember 21-year-old Tabitha Stepple, whose body was found early Thursday morning along Highway 2 near Claresholm. She had been gunned down by Derek Jensen, who police say flew into a jealous rage after seeing Stepple out with her friends last Wednesday night.

After Stepple's white, flower-covered casket was wheeled into the church in Lethbridge, her sister, Teresa Kleinfeld, remembered the young woman as someone who had an impact on everyone she met.

"Tabitha was incredibly full of life. She carried herself well," said Kleinfeld as her brothers Nelson and Trevor Stepple stood beside her. "She stood up for herself and for what she knew to be right and what she believed in.

"She was many things to many different people."

Among the mourners was Stepple's dog, Mya, who was listed as an honorary pallbearer at the service. The terrier sat in the arms of a family member.

Stepple's brother Nelson remembered his sister as someone who always looked out for him.

"Tabitha we love you. We will always miss you. We will never forget you and we will carry you in our hearts always," he said.

Her mother, Renae, read a poem.

"I'm everything you feel, see or hear. My spirit is free, but I'll never depart as long as you keep me alive in your heart," she read.

"I loved my Tabitha so much. I just want to thank you all for coming here to be with Tabitha," she said.

A book of remembrance was displayed at the church that included photos of the young woman dating back to when she was a baby. A video was also played during the service showing Stepple dancing and smiling for the camera.

Pastor Ian Lawson, one of two ministers who officiated, said Stepple's death was "so tragically wrong. Our kids are not supposed to go before us."

Lawson told CTV News that a young woman's death spurs many questions among friends, family and the community at large.

"How could this happen, where was God, what is happening to our community? Those are some of the questions that naturally come to people," Lawson said. "And those are hard questions to process, they're not easy to try to answer. In fact, I'm not sure there's a really clear answer."

Pastor Steve Bateman asked mourners to pray for the other victims of the shooting.

Stepple and her friend Shayna Conway had been driving Stepple's friends Tanner Craswell and Mitchell MacLean to the Calgary airport when Jensen ran them off the road with his car.

Witnesses say Jensen flew into a jealous rage when he ran into the group at a Lethbridge bar, where they had been celebrating Craswell's birthday. He later spotted their car at a convenience store and followed them onto the highway, police say.

Jensen had three loaded guns in his vehicle.

Police say Jensen shot and killed Stepple, Craswell and MacLean, before turning the gun on himself. Conway, 21, is the only survivor, and remains in hospital.

Craswell, 22, and MacLean, 20, were honoured Monday with a big game of catch at their former high school in Charlottetown, Colonel Gray High School, where they were once star baseball players.

Stepple and Conway had been driving the boys to the airport so they could catch a flight home to Prince Edward Island for Christmas.

Jensen and Stepple had broken up a few months before the shooting. RCMP Sgt. Patrick Webb told reporters last weekend that investigators were examining "a domestic-violence, jilted-boyfriend motive" in the slayings.

Outside the church, Stepple's friends paid emotional tributes to the young woman.

Nicole Boehr, who worked with Stepple at a Montana's restaurant that closed Wednesday afternoon so employees could attend the service, called her friend "a happy girl."

"She always made you feel good," Boehr said through tears.

"Somebody that special, you just don't lose," said Ashley Santangelo. "It's really, really hard to imagine Tabs not being here. It's definitely something that's going to be hard to live with."

With files from The Canadian Press and a report from CTV Calgary's Terry Vogt