A Chinese fighter jet crashed in coastal province of Shandong, killing two pilots.

According to the state-run Xinhua News Agency, a People’s Liberation Army Air Force Su-27 fighter aircraft went down near a beach off the coastal city of Rongcheng on Sunday afternoon while performing a drill. The cause of the accident is still unknown.

Photos and videos of the accident quickly made their way around the Web, being shared mostly on China’s Twitter-like social media platform, Weibo. The Global Times is reporting that images of the two planes show missing cockpit canopies in both, suggesting that the pilots had ejected prior to the crash, making it unclear why they did not survive.

Not until after the images were shared widely did China’s Defense Ministry confirm that the jet crash had killed the two pilots.

According to Xinhua, China has acquired 40 Su-27 fighter jets from Russia since 1992. The aircraft are typically flown only by advanced “third-generation fighter pilots” and are equipped with beyond-visual-range capabilities. These particular planes were the subject of a minor dispute when a 2006 aircraft deal was canceled by the Russians after they discovered that China had reverse-engineered and locally manufactured Su-27-like aircraft on their own.

New Chinese President Xi Jinping recently made a trip to Moscow his first international visit, meeting President Vladimir Putin. Rumors then emerged that the two nations signed a deal for China to purchase 24 jets and four submarines. After Chinese state media announced the deal, Russian state media published a report which cited a close source to Russia’s military denying the story.

Russia's experience with the previous aircraft deal and fears for the intellectual property of systems on the new aircraft reportedly stalled the deal. Some Chinese netizens have expressed reservations as well.

"Maybe the [Russian fighter jet] deal actually is a bad idea," one user wrote on Weibo.

"Do we know what happened? Was it the plane or the pilots' fault?" another user questioned.