BIG BEND NATIONAL PARK, Texas (AP) _ At least two snipers, firing from Mexican cliffs along the Rio Grande, opened fire on three rafters, killing one and wounding the other two, authorities said Sunday.

The river guide walked through thick brush after Saturday's attack in southwestern Texas, and was seen by a farmer when he reached a highway on Sunday morning. A woman who was shot hid in brush overnight.

U.S. and Mexican authorities flew over the area in a helicopter and spotted the dead man's body on the riverbank, said Mike Cox, a spokesman for the Texas Department of Public Safety in Austin.

Cox said it was the second time this year that American tourists in the area have reported being shot at from Mexican bluffs.

Between 20 and 30 shots were fired, Cox said, adding that the area where shell casings were found was remote and reachable only by boat or helicopter and was once notorious for its marijuana cultivation.

The casings were 30-30 caliber, which are used in rifles; .44-caliber Magnum; and .22-caliber, Cox said.

''The woman says it was a nightmare,'' Cox said. ''There was no provocation or anything. It was just an attack. They were just a married couple who were tourists in the area. The woman believed that two people were on the bluff. The guide said he saw four.

''They were in an area of high bluffs on the river,'' Cox said. ''The woman said she remembered seeing some smoke coming from the high bluff on the Mexican side of the river ... and that moments later, shots were fired and bullets hit on either side of their raft.''

Guide Jim Burr, 36, had led the raft about two miles downriver from a remote camp area when the shooting began about noon Saturday.

''They were in what is known as Colorado Canyon on the American side of the river in an area about 30 miles east of Presidio,'' Cox said.

Burr was shot first, in the right thigh, but managed to get the raft to shore, where all three got out, Cox said.

The snipers continued shooting, and the three got back into the raft and went farther downstream, Cox said.

''He (Burr) thought he could get to a better point of safety, so they got back in the raft and hugging closely on the shore (continued) to get on down the river,'' Cox said.

As the shots continued, the trio pulled ashore again to seek shelter in the brush. As they were getting out of the raft, Jamie Heffley was shot in the left side and left shoulder, Cox said. Her husband, Michael W. Heffley, 40, was trying to help her to safety when he was shot in the back and killed, Cox said. The injured were taken to Brewster Memorial Hospital in Alpine, about 80 miles from the national park, where night supervisor Joyce Rutledge said late Sunday they were in stable condition.

U.S. and Mexican officials were working together to find the snipers.

The Heffleys were from Eastland, about 60 miles east of Abilene, Cox said.