Thousands of police officers filled the lawn of Parliament Hill on Sunday to remember their fallen colleagues at the Peace Officer's Memorial Service.

The names of 51 officers who died in the line of duty are etched onto the memorial wall at the site, with four new names this year.

"The whole police force feels like a family when you do this," said Const. Alain Galipeau.

Among those names on the monument is Erik Czapnik, the Ottawa police officer who was killed in December of 2009 and is still on the minds of his colleagues.

"When Erik was murdered. . . we hadn't had an officer killed two decades before that," said Ottawa police chief Vern White.

The father of four was stabbed in the neck as he sat outside the Ottawa Hospital's Civic Campus. He had been with the Ottawa police for three years.

"It's still very difficult for people to this day," said Const. Brian Bonderud.

That pain will be refreshed later this year when Kevin Gregson faces charges of first degree murder in November for Czapnik's death.

In the meantime, families of police officers said it helps them and their children to prepare in case tragedy strikes them personally.

"(It helps to) have the kids see what the policing life is all about," said Karen Shah.

With a report from CTV Ottawa's Stefanie Masotti