“This is pretty typical for them, to hop on breaking news like this,” said Jonathon Morgan, chief executive of New Knowledge, a company that tracks online disinformation campaigns. “The bots focus on anything that is divisive for Americans. Almost systematically.”

One of the most divisive issues in the nation is how to handle guns, pitting Second Amendment advocates against proponents of gun control. And the messages from these automated accounts, or bots, were designed to widen the divide and make compromise even more difficult.

Any news event — no matter how tragic — has become fodder to spread inflammatory messages in what is believed to be a far-reaching Russian disinformation campaign. The disinformation comes in various forms: conspiracy videos on YouTube, fake interest groups on Facebook, and armies of bot accounts that can hijack a topic or discussion on Twitter.