As Hillary Clinton and her supporters celebrated a resounding triumph following a series of primary contests Tuesday that effectively sealed the Democratic nomination for the former secretary of state, fans of Vermont Sen. Bernie Sanders took to social media platforms Wednesday with rage and disappointment. Several Sanders fans went so far as to make threatening calls to reporters from the Associated Press, according to a report in trade publication Poynter.

AP journalists were the first to call the race for Clinton Monday night after confirming with enough delegates and superdelegates to push her over the threshold needed to win the nomination. After the story was published, several reporters received threatening calls, emails and posts on social media from people identifying themselves as Sanders supporters. In response, leaders at the AP issued security guidance to their team via email, urging staff to be aware of their surroundings.

“We have not received any specific security threats,” AP’s vice president for global security Danny Spriggs said in an email to employees, according to Poynter, noting, “It is always good to practice situational awareness around AP bureaus and offices.”

Bernie Sanders Sen. Bernie Sanders speaks at a campaign rally in Irvine, California, May 22, 2016. Photo: REUTERS/ALEX GALLARDO

Many Sanders supporters expressed anger that the AP had used superdelegates in their tally when they declared Clinton victorious Monday. Sanders himself has frequently criticized the superdelegate system, accusing it of unfairly favoring the establishment candidate.

Despite the controversy over superdelegates, Clinton called for Democrats to rally together to defeat likely Republican nominee Donald Trump. In a speech following strong primary results in California, New Jersey and New Mexico, Clinton claimed the nomination Tuesday as the first woman to be the presidential nominee for a major U.S. political party.

Tonight caps an amazing journey — a long, long journey,” she said at a rally in Brooklyn. “We all owe so much to those who came before, and tonight belongs to all of you.”