Three men who attempted to hijack a passenger plane in northwestern China in June were sentenced to death on Tuesday while a fourth man was handed a life sentence, state-run media reported on Wednesday. Two other attackers died of their injuries after the hijacking attempt.

The incident happened on June 29 aboard Tianjin Airlines flight 7554, an Embraer E190 (B-3171) carrying 92 passengers and nine crew members when it took off from Hotan Airport in China’s Xinjiang Uygur autonomous region. The aircraft was en-route to the regional capital of Ürümqi when the violent hijack attempt took place.

According to the Intermediate People’s Court in Hotan Prefecture, a group of six men had managed to smuggle explosives on board the aircraft and used converted metal crutches as weapons when they attacked the cockpit while the aircraft was about 870 miles (1,400 kilometers) from its destination.

The state-run Xinhua news agency said the attackers loudly shouted religious extremist cries, hit the cockpit door and physically and verbally assaulted the flight crew and passengers. They were eventually stopped by crew members and passengers who fought back when the attackers were trying to detonate their explosives.

Twenty-four crew members and passengers were injured in the fight while two of the attackers, identified as Ababaykeri Ybelayim and Mametali Yvsup, later died of their injuries. Their exact motivation remains unclear, but Xinhua said the group had been influenced by religious extremists.

Three of the surviving attackers, Musa Yvsup, Arxidikali Yimin, and Eyumer Yimin, were sentenced to death on Tuesday after they pled guilty. Alem Musa, who also participated in the hijacking attempt but whose role was smaller when compared to the others, also pled guilty and was sentenced to life imprisonment.

But while the exact motive of the hijacking attempt remains unclear, the incident came only days before the anniversary of violent clashes between Uighur Muslims and Han Chinese in July 2009, leaving 197 people killed and more than 1,700 others injured. The riots were the region’s worst ethnic clashes in decades and the violence only stopped when a large number of troops were deployed in the remote western region.

Following the riots, China cut all communications from the region to the rest of the world, including international phone calls, text messaging, and the Internet. Thousands of additional security forces have since been deployed and thousands of “riot-proof” closed-circuit television cameras have been set up in public places in an attempt to discourage any violence or unrest.

An estimated eight million Uighurs are now living in the Central Asian region of Xinjiang. A large number of Uighur are reportedly unhappy about the large migrant Han Chinese settlers, accusing them of making their interests less important and generally disregarding their culture.