The Note's Must-Reads are a round-up of today's political headlines and stories from ABC News and the top U.S. newspapers. Posted Monday through Friday right here at www.abcnews.com

Compiled by ABC News' Jayce Henderson and Carrie Halperin

BOSTON ATTACK: ABC News: " Obama Vows 'We Will Find Out Who Did This'" President Obama vowed today that whoever is responsible for the bombing that killed at least three people at the Boston Marathon "will feel the full weight of justice." "We still do not know who did this or why, and people shouldn't jump to conclusions before we have all the facts, but make no mistake, we will get to the bottom of this, and we will find out who did this," Obama said, offering condolences to victims and their families and praising first responders. LINK

The Boston Globe's Mark Arsenault: " 3 killed, more than 130 hurt by bombs at Marathon" Two bomb blasts, 12 seconds apart, rocked the finish line of the 117th running of the Boston Marathon Monday, killing at least three people, including an 8-year-old Dorchester boy, wounding more than 130, and leaving the sidewalks of Boylston Street covered in blood. Medical professionals on hand to care for blisters and sore knees in Copley Square suddenly found themselves treating life-threatening lacerations and lost limbs, as a high holiday in Boston, Patriots Day, turned into an epic tragedy. LINK

The Washington Post's Scott Wilson and Peter Finn: " In Boston attack, a reminder of the difficulty in foiling terrorist plots" After nearly a dozen years of foiled plots, the United States on Monday suffered the first large-scale bombing since the attacks of Sept. 11, 2001, opened an era of heightened security affecting nearly every aspect of American life. The disruption of those plots underscores the enormous strides that the American national security apparatus has taken, including the adoption of policies that remain the subject of intense concern among human rights and civil liberties groups. LINK

Politico's Josh Gerstein and Katie Glueck: " Boston Marathon explosions: Sources: Foreigner is 'person of interest'" Law enforcement is investigating a foreign national in connection with Monday's powerful twin bombings at the Boston Marathon, POLITICO has learned. The foreigner, who was badly burned, was in the United States on a student visa and is considered a person of interest and possible suspect in the case but has not been formally charged or arrested. LINK

The New York Daily News' James Warren: " President Obama vows to find those behind Boston Marathon bombing" President Obama quickly pledged "every single federal resource necessary" to Boston in the wake of the bombings at the marathon, while underscoring that as of early Monday evening he did not know "who did this or why." "But make no mistake," he said in the White House briefing room, "we will find out who did this, why they did this. Any responsible group will feel the full weight of justice." LINK

The Hill's Russell Berman: " Intelligence panels to be briefed" Members of the House and Senate Intelligence panels will be briefed by the FBI on Tuesday about the Boston Marathon bombing that left at least two dead and dozens injured. Rep. C.A. "Dutch" Ruppersberger (Md.), the ranking Democrat on the House Intelligence Committee, told reporters that members of the panel had received an initial briefing from James Clapper, the Director of National Intelligence, about an hour-and-a-half after the afternoon attack. LINK

GUN CONTROL: The Washington Times' David Sherfinski: " Senators draw the line at private gun sales" With chances iffy for winning a broad expansion of background checks in the Senate this week, gun control advocates face a tough choice: Hold out for a wide-ranging bill and risk killing it altogether, or find the stomach for a watered-down approach that ensures at least something passes. Many of the groups had hoped the bill, which hit the Senate floor Monday, would expand background checks to virtually all firearms sales. But a compromise drawn up by two gun rights supporters and blessed by Democratic leaders is slimmer, expanding checks to sales at gun shows and on the Internet, but not to all private transactions. LINK

IMMIGRATION: USA Today's Alan Gomez: " Senate immigration bill offers status, boosts borders" The federal government could pump an additional $7 billion into securing the border with Mexico, the nation's 11 million unauthorized immigrants could become U.S. citizens in 13 years or less, and the country's legal immigration system would be fundamentally altered under a bill by a bipartisan group of senators to be filed Tuesday. The group of senators known as the Gang of Eight have been working on the bill for more than two months and will announce their final measure during a press conference Wednesday. They had planned to release it Tuesday, but Sen. Charles Schumer, D-N.Y., said they delayed it out of respect for the victims of the Boston Marathon bombing. LINK

The New York Times' Ashley Parker: " Immigration Overhaul Proposal Is Likely to Ignite Fierce Debate" The introduction of sweeping immigration legislation on Tuesday is likely to ignite a months-long battle between those who want citizenship for the nation's 11 million illegal immigrants and opponents who view such an approach as amnesty. A bipartisan group of eight senators plans to unveil legislation, drafted largely in secret, that would provide a 13-year path to American citizenship for illegal immigrants who arrived in the country before Dec. 31, 2011, but would demand that tougher border controls be in place first. LINK

ECONOMY: Bloomberg's Pratish Narayanan & Jonathan Burgos: " Asian Stocks Drop With Oil as Gold Touches Two-Year Low" Asian stocks fell and Brent crude traded below $100 for the first time since July on signs growth is losing momentum in the U.S. and China. Gold touched a two- year low before rebounding from its biggest slide in three decades, while copper and the Australian dollar rose. The MSCI Asia Pacific Index (MXAP) slid 0.4 percent as of 1:16 p.m. in Hong Kong. LINK

EPA: The Los Angeles Times' Neela Banerjee: " EPA: U.S. greenhouse gases drop 1.6% from 2010 to 2011" The Environmental Protection Agency says greenhouse gas emissions in the United States showed a 1.6% decline from 2010 to 2011. The decrease continued an overall decline in U.S. greenhouse gas emissions, down 6.9% since 2005. The EPA said the drop from 2010 to 2011 is driven mostly by power plants switching from coal to natural gas, which emits less carbon dioxide when burned. Additionally, a mild winter in the south Atlantic region of the U.S., where much of the heating is electric, resulted in lower electricity demand. LINK

TAX REFUNDS: The Wall Street Journal's John McKinnon: " Tax Refunds Fall Due to Fiscal-Cliff Deal" The January budget deal to avoid the "fiscal cliff" has delayed refunds and boosted tax collections, helping to narrow the budget deficit and possibly giving lawmakers more time to craft an agreement to increase the federal government's debt ceiling. As of April 5, the number of refunds issued fell more than 2 million, or about 3.2%, compared with the number filed by around the same date last year, the Internal Revenue Service said Monday, as many Americans were rushing to file their forms by the midnight deadline. LINK

ABC NEWS VIDEO: " President Obama: Marathon Explosion a 'Senseless Loss'" LINK

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