NEW YORK -- Jewish communities are on high alert as police investigate a string of antisemitic attacks in New York City . According to NYPD, there have been at least three separate hate crime incidents in different Brooklyn neighborhoods over the last week, CBS2's Andrea Grymes reported Friday. Video shows a Jewish man walking with two kids when someone runs up from behind and hits him in the back of the head. It happened May 7 on Roebling Street between Lee and Division in Williamsburg . "It makes me feel first of all unsafe," said Elchanan Teitz, a Crown Heights...