BILL PENNINGTON, The New York Times. reports:

Pat Tillman, whose decision to give up a lucrative N.F.L. career to join the Army Rangers made him one of the most public examples of patriotism in the aftermath of the attacks of Sept. 11, 2001, was killed Thursday “when his patrol vehicle came under attack,” the Pentagon said in a statement released last night.

Tillman, 27, was a specialist assigned to the Army’s Second Battalion, 75th Ranger Regiment. It was the first American casualty in Afghanistan since March 18.

Military officials in Kabul said yesterday that his unit was patrolling one of the most dangerous areas of Afghanistan, close to the Pakistani border, in a valley where Al Qaeda and Taliban forces are known to cross into Afghanistan from Pakistan. American forces have been on special alert in recent weeks, watching for Al Qaeda and other fighters escaping an operation by Pakistani forces on their side of the border.

Tillman joined the Army in June 2002, spurning a three-year, $3.6 million contract offer from the Arizona Cardinals. Tillman, a safety and one of the team’s most popular players, had told friends and teammates that the events of Sept. 11 inspired him to try to contribute directly to the antiterrorism effort. Tillman, who enlisted with his brother, Kevin, shunned all interviews throughout his time in the Army, even late last year, after he returned from a tour of duty in Iraq.

“He and Kevin were very proud to be Rangers,” Dave McGinnis, who was his coach when he played with Arizona, said yesterday. “But he was adamant that he did not want to be singled out from all of his brothers and sisters in the armed forces. He did not think he was doing anything different than they were doing.”

McGinnis said he last saw Tillman in December, when Pat and Kevin attended a Cardinals game in Seattle. The Tillmans, who were stationed at Fort Lewis in Washington State, met privately with the team and spoke for hours with McGinnis the night before the game. They avoided reporters after the game by leaving the locker room through a side door.

“He seemed very happy to be around the team again, and Pat had every intention of coming back into the N.F.L when his time with the Army was complete,” McGinnis said. “As he left that day, he thanked me for letting him come by and I said, `No, Pat, thank you.’ That’s the last thing I said to him.”

Tillman becomes the most high-profile casualty of the American war effort in Afghanistan and Iraq. It was not clear when Tillman went to Afghanistan. He and his wife, Marie, would have celebrated their second anniversary next month.

After completing Ranger training, he served in Iraq with the elite 75th Ranger Regiment. In an interview earlier this year, the Tillmans’ father, Patrick Tillman Sr., said his sons would not tell him much about their time in Iraq.

The Tillmans’ desire to avoid publicity when it came to their service in the Army was evident early: they drove to Denver from Phoenix to enlist, believing that Army officials in Colorado would be less likely to recognize the Tillman name than those in Arizona. Pat Tillman had been a star at Arizona State before joining the Cardinals in 1998. Kevin Tillman was also a professional athlete, playing in the minor leagues of the Cleveland Indians’ organization.

Pat Tillman had long ago established a reputation as a hard-hitting overachiever who longed to do more with his life than play football. “Forrest Gump with smarts,” a college teammate called him. “He has to do everything the right thing and the extraordinary thing.”

An undersized linebacker at Arizona State, Tillman was an avid rock climber, and he was known to sneak into the university’s football stadium after hours so he could scale the 200-foot light towers. Tillman said the perch at the top of the towers was a good place to meditate.

Though named the Pacific-10 Conference Defensive Player of the Year as a senior at Arizona State, Tillman was not deemed a top pro prospect because he was only 5 feet 11 inches and 200 pounds. McGinnis scouted Tillman and thought he had a chance to make the transition from linebacker to safety.

“I remember we went to work him out for 15 minutes,” said McGinnis, who was fired by the Cardinals at the end of last season and is now an assistant coach with the Tennessee Titans. “The workout ended up taking 45 minutes, because Pat wouldn’t let us stop the drills until he did every one perfectly.”

The Cardinals selected Tillman in the seventh round of the 1998 draft (the 226th pick over all) and he became an immediate success as a special teams player. Popular with his teammates, he also stood out for other reasons. He did not own a car, choosing instead to ride a bicycle to the Cardinals’ training complex each day. He had shoulder-length hair that flowed out of the back of his helmet when he ran. In the locker room, he was noted for his diligence in the weight room and for engaging his teammates in lengthy philosophical discussions on a variety of cultural topics.

He became a starter midway through his rookie season and by 2000, when he set a team record with 224 tackles, Tillman was respected enough in the league that the Super Bowl champion St. Louis Rams offered him a $9 million, five-year contract. Tillman rejected the offer, saying that he wanted to be loyal to the Cardinals because they had given him a chance out of college. He played that season for $512,000.

Arizona players and coaches said the Sept. 11 terrorist attacks had affected Tillman deeply. McGinnis said he had not been entirely surprised when Tillman came to him in May 2002 and informed him of his plan to enlist in the Army. Tillman had just returned from his honeymoon.

“But I wasn’t shocked,” McGinnis said. “The essence of the man was to help somewhere else if he felt he was needed to help.”

The United States military in Kabul said that the death occurred about 7:30 p.m. Afghan time Thursday; two other Americans were also wounded and an Afghan soldier was killed in the clash.

Part of a coalition combat patrol, the soldiers were near the village of Spera, southwest of their base in the town of Khost. When attacked, the coalition patrol returned fire, according to a United States military statement released in Kabul. The enemy forces broke contact, and it is not known if any enemy soldiers were killed or wounded in the clash.

One of his closest friends from Arizona State, Denver Broncos quarterback Jake Plummer, said: “Today is a very sad day. My condolences go out to Pat’s family and wife. We lost a unique individual that touched the lives of many with his love for life, his toughness, his intellect and the many unique qualities he possessed. Pat Tillman lived life to the fullest and will be remembered forever in my heart and mind.”

The White House issued a statement of sympathy, praising Tillman as “an inspiration on and off the field.”

Jets cornerback David Barrett played with Tillman at Arizona for two years. “It is a tragedy that it had to happen to one of the finer guys in life,” he said. “What other person do you know would give up a life in the N.F.L. to defend what he believes in with his own life?”

Randy Zimmer, who coached Tillman in high school, said he saw Tillman at a wedding last summer. “He was feeling everyone was making a big deal of it, and he hadn’t seen a lot of action,” Zimmer said, adding that Tillman had told him, ” `I haven’t even fired my weapon yet.’ ”

Last year, the Tillman brothers won the Arthur Ashe Courage award at the ESPY Awards. They declined to attend the ceremony.

Carlotta Gall in Afghanistan and Carol Pogash in San Francisco contributed reporting for this article.