Two people were killed on Sunday night by “an unknown number of subjects in camouflage clothing armed with rifles” that ambushed a truck carrying undocumented immigrants near the U.S.- Mexico border, according to the Pima County sheriff’s department.

The shootings occurred in Eloy, Arizona in an area northwest of Tucson “that is commonly used for human smuggling,” according to a statement made available to the press by the Pima County Sheriff’s office. Authorities identified one of the victims as Gerardo Perez-Ruiz, 39, of Toluca, Mexico, and the second victim was believed to be from Guatemala.

“We’re looking at the motives and who the suspects could have been,” Pima County Sheriff’s Deputy Dawn Barkman told UPI.com. “We’re not going to speculate on any reasons for this crime at this time.”