Apalachee High School math teacher Cristina Irimie was celebrating her birthday with her students the day she and three others were fatally shot in Wednesday's mass shooting.

"She decided to bake a cake and bring pizza to her class the day she died so she could celebrate her birthday with her kids," grieving friend Corneliu Caprar told CNN.

Irimie and her husband couldn't have children of their own, so she considered her students her kids, the pal said.

The Romanian-born educator had turned 53 earlier, in August.

Irimie, who immigrated to the US more than 20 years ago, was known for her smile, her vibrant personality and her passion for her teaching -- which to her was not just a job, but a calling, friends said.

"The first thing you see is her big smile. She was always smiling," Father Nicolae Clempus, pastor of St. Mary's Romanian Orthodox Church in Dacula, told Fox 5 Atlanta.

Clempus said Irimie's husband is grieving the loss of his beloved wife in private.

"He's definitely devastated and heartbroken. They were together all the time, having a very nice and beautiful family life," the priest said.

"There's no logic in this kind of tragedy," he said of her senseless death but adding that she would live on in the hearts of her church family and others who knew her.

"We consider her a hero. Somebody that we're going to remember and look to as a role model for our generations."