Officials in Chihuahua, Mexico are still trying to sort out a tragic event involving a monster truck that hit a crowd of spectators this past Saturday, killing eight and injuring 79. Out of the 28 who required hospitalization, 12 were listed under “delicate but stable condition” and four were placed under critical condition, according to Chihuahua Mayor Marco Quezada.

Francisco Velazquez, the driver of the monster truck, has been detained on suspicion of manslaughter. Witnesses who saw the accident recall Velazquez’s helmet coming off after the truck initially hit the two cars involved with the show. After hitting the ground and picking up speed, the demolition vehicle barreled into a crowd of onlookers who were not protected by a barrier.

Authorities are also investigating a possible mechanical failure, in addition to safety concerns such as protective barrier requirements, the Associated Press reports. Velazquez was also given a blood alcohol test that he reportedly passed. Four of the spectators who lost their lives in the accident were children.

The three-day event, known as the Extreme Aeroshow, was canceled after the second day, as Chihuahua Governor Cesar Duarte Juarez called for three days of mourning. Hospitals around Mexico have started putting out requests for blood donations.