the border from El Paso , Texas , a police commander was gunned down in front of his home . The weapon used to kill Cmdr. Francisco Ledesma Salazar is believed to have been a .50 - caliber rifle . The guns are illegal to purchase in Mexico but can be obtained just north of the border at gun shows and gun shops in the United States . ATF special agent Tom Mangan says the .50 - caliber rifle has become one of the `` guns of choice '' for the drug cartels . The weapon fires palm-sized .50 - caliber rounds that can cut through just about anything . Mangan showed CNN the power of the rifle on a gun range near Phoenix , Arizona . The weapon , a Barrett , was seized in an ATF raid . A round fired from 100 yards away tore through a car door and both sides of a bulletproof vest like those used by Mexican police . `` There 's nothing that 's going to stop this round , '' Mangan says . The rifle was intercepted as it was being smuggled into Mexico . Mangan says investigators believe four others
JUAREZ , Mexico -LRB- CNN -RRB- -- A deadly trade is occurring along the U.S. border with Mexico , federal officials say -- a flood of guns , heading south , used by drug thugs to kill Mexican cops . Authorities recently seized these .50 - caliber bullets , already belted to be fed into a machine gun . In Mexico , guns are difficult to purchase legally . So , officials say , weapons easily purchased in the United States are turning up there . `` The same routes that are being used to traffic drugs north -- and the same organizations that have control over those routes -- are the same organizations that bring the money and the cash proceeds south as well as the guns and the ammunition , '' says Bill Newell , a special agent with the U.S. Bureau of Alcohol , Tobacco , Firearms and Explosives . Police in Mexican border towns fear for their lives , and with good reason . Five high-ranking Mexican police officials have been killed this year in what Mexican officials say is an escalating war between police and drug cartels . In Juarez , Mexico , just across