The Jordanian police captain who went on a killing spree, killing two American trainers in Jordan, was buried on Thursday while thousands chanted, “Death to America”.

Anwar Abu Zaid, a Jordanian police captain and co-trainer at the King Abdullah Training Centre near Amman, shot dead two US civilians contractors, a South African and two Jordanian nationals on Monday at a US-funded security training facility near the capital of Amman, Jordan. Zaid was shot and killed in the ensuing gun battle. The two Americans killed in Monday’s attack worked for the US State Department’s International Narcotics and Law Enforcement Affairs Bureau training Palestinian security forces.

Zaid’s brother, Fadi, led 3,000 mourners in the procession. He addressed the crowd, accusing the government misinforming the public about the events that led to his brother’s death and demanded that security camera footage be released.

The investigation into the incident is ongoing and the motives behind the attack are still unclear. There is much unrest among Jordanians over their government’s prominent role in fighting the Islamic State (ISIS), which increased significantly after a video of a Jordanian pilot being burned alive was released last January. Security has been increased around Jordanian government offices and American facilities in the country.

Jordan is a key American ally. More than 10,000 US ground troops and special operations forces troops are stationed in Jordan, which serves as a training, operations and logistical center for US missions in Iraq and Syria. The US Central Command Forward-Jordan was established outside Amman.