Former Vice President Joe Biden’s left eye filled with blood while he was onstage Wednesday during a CNN town hall on climate change, apparently from a burst vessel.

Biden was in the middle of speaking when his eye appeared to fill with blood, and he seemed not to notice.

The incident instantly gained attention on social media.

Ummm, is Joe Biden okay? His left eye is completely bloody…pic.twitter.com/Qq38vdO0pF — Students For Trump (@TrumpStudents) September 5, 2019

Uh, hey guys. Joe Biden’s eye filled with blood while onstage at the CNN town hall.

This is not a photoshop: pic.twitter.com/kJRHxMP8wc — Benny (@bennyjohnson) September 5, 2019

Afterwards, Biden tweeted, “We can’t turn a blind eye to the way in which environmental burdens are distributed unevenly along racial and socioeconomic lines”:

We can't turn a blind eye to the way in which environmental burdens are distributed unevenly along racial and socioeconomic lines. Biden will right these wrongs and stand up to fossil fuel companies who disproportionately harm communities of color and low-income communities. — Joe Biden (@JoeBiden) September 5, 2019

Biden, 76, has already been facing questions over his age and health amid a string of verbal gaffes and mixing up details of a dramatic story involving three separate incidents related to Afghanistan. Biden also has a long history of health issues, including multiple aneurysms.

Wednesday night’s event was a seven-hour town hall on climate change, during which ten candidates laid out their plans for climate change. The event began at 5:00 p.m. ET, and Biden did not speak until after 8:00 p.m. ET.