West Memphis, Ark. ? Two police officers doing anti-drug work were fatally shot by two men with AK-47s along a busy Arkansas interstate on Thursday, and the suspects later died in a shootout that injured the local sheriff and a deputy in a crowded Walmart parking lot, authorities said.

Officers pulled over a white minivan with Ohio license plates while “running drug interdiction” on Interstate 40 in east Arkansas, said West Memphis Police Inspector Bert Shelton. Two men got out of the van with the assault rifles and opened fire on the officers, he said.

Sgt. Brandon Paudert, 39, the son of West Memphis’ police chief, died at the scene and Officer Bill Evans, 38, died at a hospital, authorities said. Evans made the initial stop, and Paudert arrived moments later as backup, Assistant Police Chief Mike Allen said.

“In what was probably only a few minutes, Officer Evans was shoved to the ground and the men in the minivan started shooting at both officers,” Allen said late Thursday. Investigators believe the van then sped away, he said.

Authorities declined to say why Evans stopped the minivan or what was found inside.

Traffic stopped as authorities searched vehicles on Interstate 40 looking for the suspects, who were spotted about 90 minutes later in the parking lot of a nearby Walmart, officials said.

Dozens of officers swarmed the vehicle after a wildlife officer rammed the minivan with his car, and both suspects were shot and killed, authorities said.

Crittenden County Sheriff Dick Busby was shot in the arm and his chief deputy, W.A. Wren, was shot in the abdomen. Wren was in critical but stable condition and Busby was listed as stable at the Regional Medical Center in nearby Memphis, Tenn., authorities said.

The two suspects haven’t been identified. Arkansas State Police spokesman Bill Sadler declined to say whether investigators knew anything about the men, but said authorities don’t believe others were involved in the shooting.

The shootout occurred not far from the Walmart, and Sadler said it was fortunate that others weren’t hurt.

“With this many people present, somebody was watching over them,” Sadler said.