Sudden dog aggression???

[Sue, Lola, Pongo & Hubby]

So we've had Pongo, our 1 year old doodle since August when he was about 7months. We also have Lola, our 6 year old doodle whom he gets along with very well. We've taken him to the dog park several times, and he did fine. I went with him today and before we even got to the entrance gate, he was snarling and lunging at every dog he saw. Luckily, I was meeting with our dog walker (also a trainer) to hang out while the dogs ran around. She saw what he was doing and immediately took over, got him to submit and calm down. She had a muzzle in her car so we put it on him and went into the park (keeping his leash on as well). After a good 20 minutes of freaking out, he did calm down, but did snarl got pretty aggressive with a few dogs up until the time we left. Where did this come from?? My dog walker recommended aggression training, which we're of course going to do...but does anyone have any additional advice we can start working on?????? Thanks in advance!

[Sue, Lola, Pongo & Hubby]

I was just going by what my dog walker was saying....like I said, I was so shocked that I wasn't thinking!!!! My sweet boy is all of the sudden being aggressive - what the heck?? I'm definitely going to do it differently when I go back on my own.