MEXICO - -- Adrian Ruiz loved to surf. He tended bar in San Francisco, saving up enough each year to go on surfing trips around the world with his friends.

The 25-year-old San Francisco resident was on one of those surfing trips this week on the Pacific coast of Mexico with his friend, Brant Helms, when they saw a shark in the water, acquaintances said Wednesday. The two surfers joked about keeping their toes out of the water.

Then Ruiz was attacked, and Helms - who at first thought his friend was joking - paddled out to save him, but the wound was too severe.

"Adrian said he knew he was going to die," said one of his friends, Bill Herrmann, his former boss and owner of the Holy Cow nightclub in the South of Market area where Ruiz tended bar until recently.

Ruiz bled to death Monday after a tiger shark ripped a 15-inch wound in his right thigh, the Guerrero state Public Safety Department said in a statement. The wound "reached from the hip to the knee, exposing the femur," the agency said.

Shark attacks are considered rare. Friday, a 66-year-old retired veterinarian was killed by a shark while training for a triathlon near San Diego.

Ruiz and Helms were among a group of American surfers who checked in Monday afternoon into the Mi Casa es Su Casa hotel on Troncones beach. About 45 minutes northwest of the beach resort of Ixtapa, Troncones is a favorite destination for surfers worldwide, who are lured by miles of golden beaches and long breaks. April marks the beginning of surfing season, and in the evenings visitors flock to the area to watch the spectacular sunsets.

The beachfront hotel has 10 bungalows surrounding a lush courtyard garden. Ruiz and his friends all left their suitcases in their rooms and headed to the beach.

"They were one of the first ones to arrive and could not wait to go surfing," said Osman Altamirano, 24, an employee at the hotel.

Around 7 p.m., Altamirano, who was working at the hotel's restaurant overlooking the beach, heard screams for help. He rushed outside and saw two surfers floating several hundred yards from the beach in what looked like a pool of blood.

One of the surfers, Ruiz, was unconscious and had a large wound reaching from the right hip to the knee. Helms was keeping Ruiz afloat and screaming for help. Altamirano grabbed Ruiz by the arms, helped carry him back to the beach and tried CPR.

"We were all shocked, there was blood everywhere, we have never seen anything like this," Altamirano said. "Everything was happening so fast."

The hotel workers called an ambulance, but Altamirano knew that it would take too long to reach Troncones. When a bystander offered to take Ruiz in his truck to the military hospital in Ixtapa, about 30 minutes away, Altamirano and Helms went along.

"I was holding his head and Brant did CPR," Altamirano said. "We were saying 'Adrian, come on, stay with us, don't leave us.' "

At the hospital, Ruiz was taken to the emergency room, while Helms and Altamirano stayed in the waiting room.

According to the Public Safety Department statement, Ruiz died several minutes after reaching the hospital "due to the loss of blood."

When they heard the news from the doctor, Altamirano said, he and Helms cried.

Mexican newspaper Despertar de la Costa quoted experts who estimated that the shark may have weighed up to 660 pounds, and said Ruiz had been attacked about 325 yards from shore.

Two weeks ago, another tourist drowned in the area. His body, which was never found, might have attracted the shark, according to the newspaper.

One local resident said there are neither lifeguards nor doctors in Troncones, and the area is often ignored by the local government.

"This would not have happened if we had a hospital," said Juliet Altamirano, Osman's sister, who has lived in the hotel for two years. She said local residents have asked the government to help set up a medical center in the area, but never got any response.

"We are shocked," Altamirano said. "This has never happened here before."

In San Francisco, a spokesman for Ruiz's family requested privacy and did not wish comment. Ruiz's co-workers described him as an adventurer who lived for surfing - and was loved by friends and customers alike.

Herrmann said Ruiz worked for him for three years before recently going to work at other bars, including the Blue Light and Nova.

"He was a great guy - he put a smile on a lot of people's faces," Herrmann said. "He surfed a lot of the year. When he could, he would go on a trip."

Ruiz worked two years at Nova Bar and Restaurant in San Francisco. "I nicknamed him Smiley," said Elliot Feldman, co-owner of Nova. "He was one of those guys, every picture shows him with a grin or a smile. He was always happy.

"He was just one of those laid-back, really nice, fun-loving, adventure-loving guys. He lived a good life."

Feldman said some customers asked for Ruiz by name to serve as their bartender and would leave if he was not working. "Everyone who met him, loved him," he said.

Ruiz "basically bartended to save money to go to Bali and went around the world to surf," Feldman said. "Whenever he got back from one trip, he started planning the next one."

• San Francisco Chronicle article