An Arizona Department of Public Safety PD officer is in stable but critical condition after being shot in the face at a traffic stop in central Phoenix Wednesday morning, just before 3 a.m.

According to reports the officer stopped a vehicle—which had excessively tinted windows, a state violation—and asked the occupants for IDs. The officer then called for backup and two additional DPS officers arrived on-scene, at which point the officer approached the vehicle again. Someone from the vehicle opened fire.

An anonymous tip led police to the suspect vehicle late Wednesday morning, and they have detained two women, one of whom is believed to have been shot in the exchange. Officers are on the lookout for three “investigative leads,” identified as Vanessa C. Martinez, 29, Danny Angel Vargas, 26, and Ramon L. Bueno, 39.

The officer, whose name is being withheld, has undergone a five-hour surgery to save his life. He has been transferred to intensive care.

The Phoenix PD, working with DPS, FBI, ATF, and U.S. Marshalls, is conducting the investigation. For more information, visit www.AZCentral.com.