PARIS — A gunman opened fire on police on Paris’ iconic Champs-Elysees boulevard Thursday night, killing one officer and wounding three people before police shot and killed him. The Islamic State group quickly claimed responsibility for the attack, which hit just three days before a tense presidential election.Security already has been a dominant theme in the campaign, and the violence on the sparkling avenue threatened to weigh on voters’ decisions. Candidates canceled or rescheduled final campaign events ahead of Sunday’s first-round vote. Investigators searched a home early Friday in an eastern suburb of Paris believed linked to the attack. A police document obtained by The Associated Press identifies the address searched in the town of Chelles as the family home of Karim Cheurfi, a 39-year-old with a criminal record.Police tape surrounded the quiet, middle-class neighborhood in Chelles, and worried neighbors expressed surprise at the searches. Archive reports by French newspaper Le Parisien say that Cheurfi was convicted of attacking a police officer in 2001.Authorities are trying to determine whether “one or more people” might have helped the attacker, Interior Ministry spokesman Pierre-Henry Brandet told reporters at the scene of the shooting.