Cincinnati - Hillary Clinton on Monday called for an end to the "madness" after the death of three law enforcement officers in Baton Rouge, Louisiana, condemning a series of recent shootings involving police and vowing to hold those who kill police officers legally accountable."They represent the rule of law itself, if you take aim at that and at them you take aim at all of us," Clinton told civil rights activists at the annual convention of the NAACP. "There can be no justification, no looking the other way."The Democratic presidential candidate condemned the killing of three Louisiana law enforcement officers, the latest in a recent string of shootings involving black men in Louisiana and Minnesota and police officers in Dallas. She said anyone who kills a police officer or acts as an accomplice must be held accountable."As president, I will bring the full weight of the law to bear in making sure those who kill police officers are brought to justice," she said.A former Marine ambushed police in Baton Rouge on Sunday, killing three law enforcement officers in the attack. Three other officers were wounded, one critically. The shooting, the fourth high-profile deadly encounter involving police over the past two weeks, added to the tensions across the country between the black community and police.Recent violence has cost the lives of eight officers, including those in Baton Rouge, and two civilians, and it has sparked a national debate over race and policing.Reforms Clinton has proposed a series of reforms to the criminal justice system, including developing national guidelines on the use of force by police, new investments in bias training, legislation to end racial profiling and funding for body cameras. She has also pushed for cutting mandatory minimum sentences, particularly for drug offences, and providing better support to help the formerly incarcerated find jobs after prison."We have difficult, painful, essential work ahead of us to repair the bonds between our police and our communities and between and among each other," she said.Clinton spoke as Republicans gathered for the first day of the party's national convention in Cleveland. Clinton referenced presumptive Republican nominee Donald Trump's decision not to speak at the NAACP convention. "My opponent may have a different view, but there's nowhere I'd rather be than right here with all of you," she said.'We are hiring'She also made a fresh pitch for campaign organisers and volunteers, telling attendees, "we are hiring."Clinton's campaign is launching a major voter mobilisation drive during the Republican National Convention, with a goal of getting more than 3 million to register and commit to vote in the 2016 election.During the week, Clinton's campaign and state Democratic co-ordinated campaigns will hold more than 500 registration or "commit to vote" events across the nation. Voter registration events will be held at the Islamic Centre of Akron's Eid celebration in Ohio; a bilingual day camp in Hazelton, Pennsylvania; Detroit's Eastern Market; and a campaign office opening in Madison, Wisconsin.Clinton is attending a rally in Cincinnati before travelling to Minneapolis to address the annual conference of the American Federation of Teachers.