Another Mexican journalist and radio host has been killed at his home in Sonora, which lies on the U.S.-Mexico border, neighboring Arizona. Unidentified gunmen shot and killed Santiago Barroso Friday, making him the fourth known reporter to be killed in Mexico this year. Shortly before his murder, Barroso reported on smugglers attempting to bring a group of migrants across the border.

Human rights and press freedom groups are calling on the Mexican government to investigate the killing and put in place measures to better protect journalists. British nonprofit Article 19 found that there is a 99 percent impunity rate for crimes against journalists in Mexico.