Shortly after Senator Bernie Sanders announced he was endorsing Hillary Clinton [1] for president and ending his campaign for Democratic candidate, Donald Trump started firing off insults on Twitter. The presumptive GOP nominee implied that Sanders was a traitor for supporting the "crooked" person he fought against throughout the Democratic primaries.

Bernie Sanders endorsing Crooked Hillary Clinton is like Occupy Wall Street endorsing Goldman Sachs.

— Donald J. Trump (@realDonaldTrump) July 12, 2016 [2]

Bernie sanders has abandoned his supporters by endorsing pro-war pro-TPP pro-Wall Street Crooked Hillary Clinton.

— Donald J. Trump (@realDonaldTrump) July 12, 2016 [3]

To all the Bernie voters who want to stop bad trade deals & global special interests, we welcome you with open arms. People first.

— Donald J. Trump (@realDonaldTrump) July 12, 2016 [4]

The Sanders Twitter account quickly fired back, calling out Trump's "big talk."

Big talk from the same guy who was too afraid to debate Bernie in California. https://t.co/LVCjo0PKrN [5]

— Bernie Sanders (@BernieSanders) July 12, 2016 [6]

The tweet was referring to the time in May when Sanders proposed a debate with Trump ahead of the California primary. The real estate mogul initially agreed to the debate on an episode of Jimmy Kimmel Live [7] but then backed out.

During the speech this morning in which he endorsed Clinton, Sanders also slammed Trump [8] — this time, for insulting many minorities in the country.