At one point, Ricky asks Dr. Bloom if he has children. Since Ricky's one rule is that he won't harm a child, he seems to be ensuring that he's not orphaning one on Christmas Eve.
The guy Ricky takes the gun from seems awfully dense for someone who "knows how to use this". Most people assume he's a cop, due to being uniformed and driving a marked car. However, looking at his uniform, there are clear markings of "Security Guard" on his shoulders. He probably is either employed by the local neighbourhood or is coming off shift from somewhere and saw a chance to be a hero. It also means that he has no training in how to actually detain a suspect; When the actual police show up (in different uniforms to the first guy) at the end of the rampage, they're wisely there in numbers and actually keeping distance from Ricky until it transpires he's out of ammo.
