A leading Republican said Friday that the unfolding events in Boston underscore the need to address “gaps and loopholes” in the nation’s immigration system, stressing that any new immigration bill should tighten screening to stop those “who wish to do us harm.”

Sen. Chuck Grassley, R-Iowa, addressed the terror attack and ongoing manhunt at the start of a Capitol Hill hearing on newly unveiled comprehensive immigration legislation. The Boston crisis rapidly overshadowed the hearing, the first held for the major piece of legislation. Homeland Security Secretary Janet Napolitano had been scheduled to testify but canceled as federal law enforcement agencies were pulled into the crime scene. Grassley, though, suggested the attacks in Boston could influence how the immigration bill is considered.