At New York's St. Patrick's Cathedral ... a mass ... in memory of two fallen NYPD officers, with Mayor Bill de Blasio and the police commissioner in attendance.<br/> <br />The two officers were ambushed and shot dead ... in what police say was an "execution".<br/> <br />They say the suspect was bent on killing officers as revenge for police shootings of unarmed black men.<br/> <br />Police say he came to Brooklyn from Baltimore, where he had also shot and wounded his girlfriend.<br/> <br />Baltimore's police union president says growing anti-police sentiment has reached crisis levels.<br/> <br />SOUNDBITE: BALTIMORE POLICE UNION PRESIDENT GENE RYAN SAYING:<br/> <br />"Not since the political unrest of the 1960's have police officers been so targeted. And I think it's important to remember that this isn't just a Baltimore or New York problem, this is a powder cage nationwide."<br/> <br />Mayor de Blasio has ordered flags flown at half staff around the city.<br/> <br />But New York's main police union is roundly criticizing hi
