Twitter is often full of short-burst, back-and-forth argument, but Clara Jeffery, the co-editor of Mother Jones, found out that the debate can turn dark after tweeting last Saturday about the death of Chris Kyle, an ex-sniper who was killed at a gun range by a fellow veteran he was trying to help. (Hat tip to Peter Sterne for putting together a list of the tweets on Storify.)

So much for good/talented guy with a gun being able to stop mentally ill guy with a gun: //t.co/6UJS0fLW — Clara Jeffery (@ClaraJeffery) 3 Feb 13

Advocates for gun rights were enraged and immediately began tweeting outrage at Ms. Jeffery. The velocity increased after her tweet was posted on Twitchy, the Twitter aggregator run by Michelle Malkin, the conservative commentator.

Many of the tweets wouldn’t meet the language standards at The New York Times, but here are a few of the more printable ones.

@ClaraJeffery Enjoying dancing on his grave to prove your point, psycho? — John Price (@JPrice02) 3 Feb 13

When Twitter Trolls Attack: should @ClaraJeffery be shot by heroic a sniper ? or just a mentally ill gun nut? //t.co/1g6kYTD4 — lil mike sf (@lilmikesf) 5 Feb 13

@HeidiL_RN advised Ms. Jeffery to “Erase those disrespectful tweets now,” suggesting if she did not, “You will regret this.”

In general, many of the tweets accused Ms. Jeffery of politicizing a tragedy immediately after it happened, but the level of threat and misogyny in the responses surprised her.

“I’m used to debating and defending what I say on Twitter and elsewhere, but in this instance there were immediate threats made on me and my family,” she said in a phone interview on Tuesday. “I felt bullied, and there were times in there where I felt worried.”

It was an odd circumstance where many were using free speech to go after someone else who was engaging in the same,as James Temple points out. Ms. Jeffery said that after the initial barrage, she received vocal support on Twitter and back-channel e-mails from people she called “prominent conservatives” who told her to “keep her chin up.”

“The anonymity of social media is important and played a big role in the Arab Spring, but in this instance people hid behind their avatars to say really hateful things,” she said. “If they scare you into not participating in the debate, then there can’t really be a debate.”