() Four people were killed when a medical transport plane crashed in Arizona on Tuesday.

The dual-propeller Beechcraft 300 went down while landing at Chinle Municipal Airport in the eastern part of the state around 12:40 p.m. local time.

The four victims were medical personnel who were set to pick up a patient from a nearby hospital, NBC News reported, citing Navajo Nation President Buu Nygren.

“These were people who dedicated their lives to saving others, and their loss is felt deeply across the Navajo Nation,” Nygren wrote.

“We honor their service, their sacrifice, and the love they showed our communities through their work.

“On behalf of the Navajo Nation, I extend my deepest condolences to their families, colleagues, and all who are grieving.”

The cause of the crash wasn’t immediately known. The FAA and the National Transportation Safety Board are investigating.