A Lab attacking? Most unusual. Sounds like Barney was even wimpier than my Lab is.
A golden lab once attacked my Irish Wolfhound, unprovoked. Big mistake - IWs were breed to run-down and kill wolves in one-on-one fights and although they are now the friendliest dog you'll ever meet, the potential for mayhem is still there. Once the IW regained his balance, he instantly overpowered the lab. Within about 5 seconds from the initial sneak attack, the lab was on its back in complete submission with the IW standing over him with bared teeth and the most threatening, rumbling growl you'll ever hear. I told people to understand the turnaround, imagine walking up to Mike Tyson in the mid-80s and sucker punching him.