Top Republican says Boston attack shows need to fix 'gaps' in immigration system 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. It's important for us to understand the gaps and loopholes in our immigration system. While we don't yet know the immigration status of the people who have terrorized the communities in Massachusetts, when we find out, it will help shed light on the weaknesses of our system," said Grassley, the top Republican on the Senate Judiciary Committee. The two suspects have been identified as Dzhokhar A. Tsarnaev, 19, and his brother Tamerlan Tsarnaev, 26, who was killed early Friday morning. The two are believed to be from the region near Chechnya. One source briefed on the matter said they are thought to have arrived in the United States about a decade ago. Police are still looking for Dzhokhar Tsarnaev. The case appeared to spark an interest by Grassley in potential legislative changes. How can individuals evade authority and plan such attacks on our soil? Grassley asked Friday. How can we beef up security checks on people who wish to enter the United States? How do we ensure that people who wish to do us harm are not eligible for benefits under the immigration laws, including this new bill before us? Democratic Sen. Charles Schumer, D-N.Y., though, cautioned that the facts in the Boston case are still coming out. He urged lawmakers to let that information emerge "before jumping to any conclusions about Boston." "I'd like to ask that all of us not jump to conclusions regarding the events in Boston or try to conflate those events with this legislation," Schumer said. Meanwhile, lawmakers proceeded to debate the immigration bill at the hearing, as senators begin the work of considering and modifying the sweeping legislation. Schumer said it would "unleash the potential of our legal immigration to create robust economic growth." Doug Holtz-Eakin, former director of the Congressional Budget Office, also said the legislation could have a major impact on the economy. "At its core, immigration reform represents an economic policy opportunity," he testified. He and others claimed the legislation could help the U.S. economy grow, by welcoming in foreign entrepreneurs and budding small business owners. But Sen. Jeff Sessions, R-Ala., citing last month's poor jobs report, claimed the changes could put Americans in direct competition with more immigrants for scarce jobs, even in low-skilled areas. This is indisputable. We have more unskilled labor than we can find jobs for today," he said. The bill would aim to boost border security, improve legal immigration programs and eventually grant citizenship to some 11 million people here illegally. The 844-page legislation was introduced around 2 a.m. Wednesday, and critics say there's been insufficient time to digest it and they've pushed for more hearings and a long process. Friday's hearing was the first of two the Judiciary Committee is expected to hold on the bill before it begins amending and voting on it next month.