TORONTO -- U.S. President Donald Trump seemed to mock 16-year-old environmental activist Greta Thunberg Monday night on Twitter, after a piercing glance from the teen at the UN climate change summit went viral.

鈥,鈥 wrote American singer and actress Bette Midler, who has been a vocal opponent of Trump on Twitter.

A short clip shared widely online shows the Swedish teen watching Trump with furrowed brow as he enters a room. Many users have dubbed it a 鈥渄eath stare.鈥

Earlier in the day, the teen made an emotional speech, which has been viewed millions of times online. 鈥淵ou have stolen my dreams and my childhood with your empty words,鈥 she said. 鈥淧eople are suffering. People are dying. Entire ecosystems are collapsing. We are in the beginning of a mass extinction and all you can talk about is money and fairy tales of eternal economic growth. How dare you.鈥

In response to the speech, Trump tweeted a about the teen: 鈥淪he seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!鈥

Thunberg returned the mockery and turned the tweet into , which now reads: 鈥淎 very happy young girl looking forward to a bright and wonderful future.鈥

But the so-called 鈥渄eath stare鈥 dominated much of the Twitter conversation after Thunberg鈥檚 speech, many tweeting support for the teen.

鈥淚 wish your death stare was accompanied by ,鈥 wrote one user. 鈥淕reta Thunberg staring straight into Trump's dark, cavernous soul,鈥 wrote another user.

Others memed the moment further, putting the word 鈥淎steroid鈥 over Thunberg鈥檚 face and 鈥淒inosaurs鈥 over Trump鈥檚.