The man suspected to have set off an explosion at Shanghai Pudong International Airport on Sunday afternoon cut his own neck with a knife afterward, Shanghai police said on their official Weibo microblog.

The man detonated a beer bottle containing unknown substances around 2:20 p.m. at the airport’s Terminal 2 check-in Area C. Four others were injured by glass shards, police said. One of the injured is from the Philippines.

He was brought to Pudong New Area People’s Hospital by ambulance and was placed under emergency care. He remains in critical condition.

The four other injured people have also been brought to the hospital and are undergoing treatment.

Security footage of the blast showed people running away before the man set off the explosive device.

Police say they are continuing their investigation.

Wang Hongwei, associate professor in public affairs at Renmin University in Beijing, told Sixth Tone that many security staff at airports around China are young and lack experience. 

But, Wang added, ultimately attacks like these are hard to prevent.

“This is not just an airport security issue, but more importantly, the potential danger in this society with high mobility,” he said. “Two years ago, there was an explosion at the Beijing Capital International Airport, and now there’s this explosion at the Shanghai airport. But how far can we push our security checkpoints?”

Additional reporting by Cai Yiwen and Fu Danni.

(Header image: A bomb disposal expert inspects luggage near the scene of the explosion at Shanghai Pudong International Airport, June 12, 2016. Aly Song/Reuters)