As others have said, they search out fellow Jews and try to get them to be more observant. It might be the “tank” but they also might just invite you to their shul or to their home for shabbat dinner.
Very likely they were doing some kind of leaf-letting of interest to Jews only. It’s happened to me at Brighton Beach.
The Lubavitchers also hang out at Santa Monica Promenade. I never know what to say in response to The Question, because I don’t want to deny my ethnic Jewishness, but at the same time I don’t want to be sucked into any religious nonsense.
Tell 'em you converted from Baptist to Reform Judaism? 
That took me a minute to see. 
Good job it wasn’t me !
I was once “clipboarded”, and asked if I smoked cigars.
An ex cigarette smoker who loathed cigars when I still smoked, I answered in the affirmative hoping to get some freebies, tight bastard that I am .
And I did.
Mind you in a similar situation I received a 45 minute sales pitch on why I should become a Scientologist.
And there, in a nutshell, you have the difference between the Jews and the Irish: two peoples whose response from the world at large has historically been “shut up.”
The Jews, an intelligent race whose survival depended on exercising their intelligence, realized that sometimes it’s best to shut up. The Irish, an equally intelligent race whose survival depended on suppressing their intelligence, simply resolved *never *to shut up.
How do you explain Robert Briscoe?
I thought you were going to pull a Samuel Johnson:
“Oats, a grain that in England is fed principally to horses, but in Scotland supports the population.”
The shofar drives the tank, right?
I just want to say that I’ve had these Jewish people pegged all wrong for such a long time. I was led to believe that they were, by and large a cerebral and mild-mannered lot.
But now I hear that they tool around the city in shofar-driven tanks, stepping up to hassle people in the park?
Where can I sign up? 
Nice spot!
I saw what you did!
My girls are blue-eyed blond Irish Jews.
I was really tempted to give them very Jewish first names to go with their very Irish last name but Yael and Chaya Very Irish Last Name sounded bizarre even to my ears.
And on Rosh Hashana, a member of the congregation blows the shofar.
He’s always hoping that next year it’ll be the cute young blonde woman, but it never seems to work out that way…
I have a Very Jewish last name that starts with an “Ah” sound.
At college (in the US) I had an Irish-descent friend, who simply replaced the “Ah” sounds with an “O” sound. It worked very well 
(imagine that may last name is something like, Oh, I don’t know, “Abama”…? :D)
No, he just hoots the horn. 