I have no sympathy with people who kill in circumstances like those, and the punishments meted out by the courts are generally not strong enough, given the effect these people have had on others lives. The issue I'm trying to raise - and, again, I'm not talking about the individual case you've cited - is that this could lead to a two-tier system of punishment: If a Canadian-born person commits a crime, they go to prison for a year, maybe get some rehab, whatever. An immigrant committing the same crime may find him/herself kicked off a plane anywhere in the world, and left to fend for themselves.
As I said, I have no sympathy for people who's selfish actions devastate the lives of others, and often the punishment doesn't fit the crime. Make the punishment a strong one, make people pay for the consequences of their actions, but make it consistent.