jack is getting very dog aggresive

[jacksonm]

Jack is getting dog aggressive but its very random he literally tried to rip a Pomeranian in half the other day while my girlfriend let him out. She let him out off leash and I kno it wasn't my neighbors fault but I k o she purposely walks her dog behind my house when jacks out. So now jack goes out on a leash unless its night. But this is where it gets fuzzy to me some times he will walk by other dogs fine sometimes a dog barking in the distance sets him off he barks at people out the window but rarely when he's on leash. I blame it on puberty sometimes as a joke but maybe that is a issue im kind of at a lost he knows the look command . I kind of give a shoosh noise like u do a baby( not the ceased Milan thing just a habit I picked up) and he looks at me and we go on our way if it gets to intense I turn him and we all the other way. But its very confusing he use to be around my girlfriends parents dog (a golden retriever) since he was a pup and there dog was full grown but now they fight. Any help on the solution would be great

[srennie]

How old is he? Is he neutered?

[Fabbidavisjr]

I would put him through another training course....if you haven't done one already. Like the post above nurturing him will slow down his testosterone a lot.