New England Patriots tight end Rob Gronkowski announced his retirement from the NFL on Sunday, saying on Instagram he's "so grateful" for the time he spent on the team.

Gronkowski, 29, played nine seasons with the Patriots, and he thanked his teammates, fans, Patriots owner Robert Kraft, and Coach Bill Belichick for their support. "Now it's time to move forward and move forward with a big smile knowing that the New England Patriots Organization, Pats Nation, and all my fans will truly be a part of my heart for [the] rest of my life," he said. A person with knowledge of the matter told ESPN that Gronkowski told Kraft about his decision in a phone call Sunday.

Quarterback Tom Brady praised Gronkowski on Instagram, calling it an "honor and privilege" to play with him. "You accomplished so much and our team was almost unbeatable when you were on the field!" he said. Gronkowski played 115 regular season games, with 521 receptions for 17,861 yards, and 16 playoff games, with 81 receptions for 1,163 yards and 12 touchdowns, records for a tight end. Catherine Garcia

Rep. Seth Moulton (D-Mass.) became the 19th Democrat to join the 2020 Democratic race on Monday, declaring the field "wide open" and saying he planned to focus on national security and defense issues. Moulton is also the third presidential candidate from Massachusetts — following Sen. Elizabeth Warren (D) and former Gov. William Weld (R) — and like South Bend Mayor Pete Buttigieg, he's an Iraq War veteran. He last made national news leading an unsuccessful leadership challenge against House Speaker Nancy Pelosi (D-Calif.).

"I'm running because we have to beat Donald Trump, and I want us to beat Donald Trump because I love this country," Moulton said in his campaign launch video. "We've never been a country that gets everything right. But we're a country that, at our best, thinks that we might." He will be on Rachel Maddow's MSNBC show Monday night and plans to hit all four early voting states this week, starting with New Hampshire on Tuesday. Peter Weber

Sri Lanka's government said Monday that a coordinated series of bombings that killed at least 290 people and wounded 500 on Sunday had been carried out by seven suicide bombers from National Thowfeek Jamaath, a little-known Islamist militant group. All the bombers and most of the victims were Sri Lankan, the government said, though authorities are investigating possible foreign links to the attack. At least 24 people were arrested.

The first six bombings hit three Christian churches holding Easter services and three luxury hotels. Among the dead were 32 foreigners from the U.S., Britain, Turkey, India, China, Portugal, and the Netherlands; Danish billionaire Anders Hoch Povlsen said three of his four children died in the attacks.

Sri Lankan Prime Minister Ranil Wickremesinghe confirmed Sunday night that security services had been "aware of information" about a possible attack on churches and had not acted on it. An April 11 domestic intelligence report seen by Reuters said a foreign intelligence service had warned Sri Lanka about possible attacks. Two government ministers also said publicly that there had been warnings, some specific to popular churches.

The Easter bombings were the deadliest incident in Sri Lanka since a 26-year-long civil war ended in 2009 between the country's mostly Buddhist Sinhalese majority and its Tamil minority, made up of Hindus, Christians, and Muslims. "While anti-Muslim bigotry has swept the island in recent years, fed by Buddhist nationalists, the island also has no history of violent Muslim militants," The Associated Press reports. "The country’s small Christian community has seen only scattered incidents of harassment in recent years." Peter Weber

Special Counsel Robert Mueller's investigators followed "several meandering paths" in their two-year investigation, "propelled by discoveries of unusual interactions between Trump associates and Russians," The Washington Post reported Sunday night. Mueller uncovered a lot in his 448-page final report, but his team was left with "some unanswered mysteries, a lot of dead ends and, ultimately, a conclusion that the contacts they found did not establish a criminal conspiracy," the Post says.

Mueller's team had to grapple with a legal dispute with Attorney General William Barr over whether a president can even be accused of crimes, plus President Trump and his son Donald Trump Jr. refused to be interviewed, and the witnesses they did have "were not ideal," the Post reports:

A few key players, prosecutors would contend, lied in interviews. Many were loyal to the president and echoed his rhetoric that Mueller's team was acting in bad faith. Some used encrypted applications with disappearing messages that could not be reviewed. Others were overseas, unreachable to American investigators. In some cases, their statements were only loosely tethered to the facts. [The Washington Post]

Ex-Trump campaign chairman Paul Manafort fits in the first three categories, and the "loosely tethered" description matches conspiracy theorist Jerome Corsi, the Post reports, citing an interview with Corsi's lawyer, David Gray. Corsi had offered "tantalizing leads" about Roger Stone and WikiLeaks, but his story was never quite straight and his leads always led to dead ends, the Post reports.

Trying to get actionable material out of Corsi, "it's their biggest nightmare," Gray told the Post. "The supposed best of the best were just frankly dumbfounded by the whole situation." Corsi was not charged, he added, because after six marathon interviews, "at the end of the day, they threw up their hands and said, 'We can't use any of this.'" Read more about the obstacles Mueller could't get over at The Washington Post. Peter Weber

John Oliver's main story on Sunday's Last Week Tonight focused on — what else? — Special Counsel Robert Mueller's report, which he framed as the latest and maybe last chapter of his "Stupid Watergate" series — "basically Watergate, but if Nixon had been kicked in the head by a billy goat, and also if that billy goat had been the White House chief of staff."

Once people actually read the 448-page redacted report released Thursday, "it became clear that there was a lot in it," Oliver said. "And some of the details in this report were incredible." The one he lingered on, with artistic license, was Trump reportedly saying Mueller's appointment marked "the end of my presidency, I'm f---ed" — except Oliver, of course, did not censor the F-word. Since "we clearly can't cover everything in the report tonight," he said, "I'd like to concentrate on two key factors that may have saved the president here": Incompetence and disobedience.

"When it comes to conspiracy, Trump's saving grace may have been that despite Russians wanting to help," his campaign and family displayed "often cartoonish levels of disorganization and incompetence," plus "ignorance of basic legal concepts," Oliver said. He said the report's findings that so many of the people in Trump's orbit just ignored his orders to potentially obstruct justice is "both reassuring and also terrifying," though worryingly, "lots of those people are gone now, and the newer figures seem very much on the same page as the president," notably Attorney General William Barr.

Barr's preemptive spin now "seems laughably and willfully misleading," Oliver said. "It's like Barr summarized the Twilight novels as: 'A girl in Florida goes to third base with a wookie.'" The parts of Mueller's report we can read may feel like a letdown, he said, but its imparted knowledge "can inform Congress going forward and, crucially, voters a year and a half from now." The clip is full of NSFW language. Watch below. Peter Weber

There are many reasons people who work in the White House are reluctant to take notes, and traditionally they center around protecting the president. But lots of people in President Trump's White House took notes for the opposite reason, report Peter Baker and Annie Karni at The New York Times: To protect themselves against "a mercurial, truth-bending chief executive who often asked them to do things that crossed ethical or even legal lines, then denied it later."

Some notes by Trump staffers have ended up as tell-all books, but Special Counsel Robert Mueller's report also drew from contemporaneous notes, shining new light on Trump's actions — and his strong aversion to note-taking, especially since he can no longer rely on nondisclosure agreements.

Mueller's team obtained notes or contemporaneous memos from former White House Counsel Don McGahn, his deputy Annie Donaldson, former White House Chiefs of Staff Reince Priebus and John Kelly, former Trump campaign chiefs Paul Manafort and Corey Lewandowski, adviser Stephen Miller, and other advisers, lawyers, and government officials. Some of them kept notes of alarming conversations with Trump in safes, according to Mueller's report.

We know Trump hated note-taking from McGahn's notes and Trump himself, who alleged in a Friday tweet that some "so-called 'notes' ... never existed until needed" and contained "total bullsh-t." Trump also publicly berated former National Security Adviser H.R. McMaster for taking copious amounts of notes, the Times reports.

W. Neil Eggleston, who served as a lawyer for President Bill Clinton and as president Barack Obama's White House counsel, told the Times he "didn't take notes when I worked with either president," but to protect the presidents, not make sure he wasn't "part of a criminal conspiracy," like Trump's aides. "To create records of information that was quite harmful to the president, that is really remarkable," he added. "And to do it and then stay on and continue to write them, is really something to me." Read more at The New York Times. Peter Weber

Every time Avery Fauth, her two sisters, and her parents visit North Topsail Beach in North Carolina, they scan the sand, hoping to spot an ancient megalodon shark tooth.

The family kept up their tradition while at the beach over spring break. As they walked along, Fauth, a middle school student from Raleigh, saw something that caught her eye. Intrigued, she went to the object, which was buried in the sand. "I uncovered it and it keeps coming, and it's this big tooth, and then I hold it up and I'm screaming for my mom," Fauth told WECT.

It was a megalodon shark tooth, and her father, who started searching for megalodon teeth 25 years ago and got his daughters hooked on the hunt, was stunned. "I was really shocked and excited for her that she found something that big," he said. The megalodon, the largest shark ever documented, went extinct millions of years ago, and Fauth's tooth could date back three million years. "They're really rare to find and they're some pretty big teeth and they're pretty cool," she said. The tooth will live in a "special box" inside Fauth's home. Catherine Garcia