Universal has purchased the spec script “Mad City,” about a disgruntled ex-employee who takes a museum and its occupants hostage as a tabloid journalist exploits the situation. The spec, written by Tom Matthews, was sold Tuesday by UTA’s Barry Mendel to U exec Nina Jacobson for a low six-figure sum against mid-six figures.For Matthews, who co-authored the story with Eric Williams, the sale is a nice going-away present. A publicist who worked on the lot at Fox for the last three years, Matthews had given notice prior to the spec sale, and leaves at the end of the week to return with his wife to Wisconsin. “I’ve been out here 15 years, and spent years cranking out screenplays with increasing interest but no sales,” he said. That changed Tuesday.