Is my puppy dangerously aggressive to my younger puppy?

I have a 7.5 week old purebred coon dog that we just got for my younger brother. And a week later, we got a 5 week old lab mix for my younger sister. The coon pup, Red, is very aggressive towards the lab, Patches. I don't know if its a problem or if they're just playing. What do I do? For the past two days every time we take Patches outside, Red attacks. We have been having to keep him inside. Please help. I can't take him to the vet because we don't have the money.