Overview (1). Nicky Cruz was leader of a brutal Puerto Rican New York gang called 'The Mau Maus' which ran wild in the mid to late 1950s, before he met the preacher 'David Wilkerson'.verview (1). Nicky Cruz was leader of a brutal Puerto Rican New York gang called 'The Mau Maus' which ran wild in the mid to late 1950s, before he met the preacher 'David Wilkerson'.