For the last sentence, he shifts into the so-called historical present. This is probably prescriptively incorrect, but it's relatively common, particularly in speech and in storytelling. The best way to analyze it is up for debate, but I think this section of the Wikipedia article captures it:
More recently, analysts of its use in conversation have argued that it functions not by making an event present, but by marking segments of a narrative, foregrounding events (that is, signalling that one event is particularly important, relevant to others) and marking a shift to evaluation (Brinton 1992: 221).
I've bolded the relevant section. Shifting into the historical present to highlight a particular section of a story is relatively common, and it doesn't literally indicate present time when it happens. Instead, it calls attention to the events, (in my interpretation) making them more vivid by putting you in the story, as though it's happening right now.
I believe that this is something that happens fluidly as people speak, often without giving much thought to it. And although we can analyze usage and find patterns, it may not be possible to nail down exactly why people do it in each case. Beyond a certain point, it becomes a matter of interpretation and how the stylistic device makes you feel as a reader or listener.
So I'd say: just be aware that it's something people do and that it's not a mistake. It's more a stylistic choice than anything else.