This is a tough one. The two kids on CTV said he was an ok guy. So, he was doing an ok job at the youth centre. Wonder if losing his job on May 18 had an impact on what happened on June 2? When you take away a person's ability to earn an honest living, you leave him with much less options to earn a living, not to mention the loss of income and self-esteem. People busy at a job usually have less time to indulge in other activities.
I doubt it happened so fast or can be explained so simply. But your point does open the discussion as to the problem that can be looked at in general. Many (including TERB posters) say its a cultural issue. I have often said it is more socioeconomic in its roots; which a certain 'group' of people have always been on the short-end in the Western world. They have always been at a disadvantage and it should come as no surprise when they are herdded into a neighbourhood that they end up doing whatever they can in order to build community (e.g. gang) and earn. It's a discussion that takes much more than a paragraph to explain, but if you search Google Scholar, you will find that much research has been done and proves that socioeconomic factors play a much larger role in people being involved in criminal activity (mostly of the violent kind) rather than any other fictitious factor which is mostly mentioned.
Generally speaking, in the Western World; minority --> low socioeconomic status --> propensity to be involved in, 'non-white-collar crime' (if a member of 'the majority' finds him/herself in a low socioeconomic situation, they too are also more likely to commit crime), and not 'minority' --> crime, as 'minorities' who have higher levels of socioeconomic status are less likely to partake in the type of activities discussed here.
Now before anyone decides to jump all over this and cite "my 'minority' friend" or Obama examples this is a correlation not a perfect science.