KABUL, Afghanistan — The man who arrived at the police chief’s home one afternoon in early February carried a piece of paper. He needed a signature, the man told the chief’s brother, handing him the document. Was the commander home?

“I took the document, and I was on my way through the house when I heard this incredible boom,” recalled Niaz Mohammad, the brother of Kandahar’s provincial police chief. “I don’t know what happened. I just blacked out.”

The car bomb explosion that crumbled Gen. Mohammad Mojayed’s home that day was but one in a relentless series of assassination attempts against Kandahar’s top police official.

He survived at least three in recent months, but Friday afternoon his luck ran out.

A man wearing a suicide vest under a police uniform slipped into the courtyard of the police headquarters and approached Mojayed as he came out of his office. The explosion killed him and two other policemen and wounded three more. The Taliban took credit for the attack.

Mojayed’s death is a major setback for American military efforts in Kandahar, the heartland of the Taliban and a focus of the U.S. counterinsurgency campaign. He was considered a brave and capable leader who had first earned his reputation in the war against the Soviets.

Unlike his predecessor, who came from eastern Afghanistan, Mojayed was a native of the lush Arghandab River valley of Kandahar province.

“He’s from here. He has influence here,” Lt. Col. John Voorhees, commander of the U.S. Army battalion that mentors the Kandahar police, said in February. “I think the Taliban is feeling threatened because of his leadership ability.”

The earlier attempts on his life were watched closely by U.S. military commanders because Mojayed was an anomaly: one of the few members of the Alokozai tribe in positions of authority in Kandahar.

Since the start of the war, certain Pashtun tribes have flourished by seizing political power and lucrative U.S. military contracts. The Popalzais, the tribe of President Hamid Karzai, have dominated Kandahar politics through the president’s half-brother, provincial council chief Ahmed Wali Karzai, while the Barekzais have become rich by building and maintaining Kandahar Airfield.

The Alokozais, despite being the third-largest tribe in Kandahar, were largely excluded from power. Mojayed had lost his job in 2004 as an army corps commander amid bitter feuds with the Barekzais. Other Alokozai leaders were killed and forced out of the province. With their exclusion from government, some Alokozais gravitated toward the Taliban.

“We’ve been given some opportunities and development projects, but those things have not been on a level that can satisfy the Alokozai tribesmen,” said Shah Mohammad, the governor of Arghandab district, a predominantly Alokozai area and one of the most violent patches of Kandahar in recent years. “Things are not getting better. Things are the same for the Alokozais.”

The selection of Mojayed as police chief last year was supported by U.S. officials as a way to move the local government toward greater inclusion. Some have argued that his tribal affiliation helped calm the Arghandab.

“When Alokozais see somebody from their own tribe representing them, they will support the government,” said Mojayed’s brother, Niaz Mohammad, who is police chief in Arghandab district.

Mojayed left a comfortable life in Kabul to take over a police force plagued by incompetence, corruption and drug use. He knew he was a marked man – in the eyes of the Taliban and also, he suggested, among rival tribes.

“Maybe there are people from other tribes who are trying to harm me or kill me, but I don’t know, I’ve never caused any problems for anybody,” he said in February. “And I think that the people who dislike me have close relations with the insurgents.”

U.S. military officials had been investigating the previous assassination attempts to determine whether the Taliban were targeting yet another government official or whether tribal motives were at play.

“The Taliban wants to get him, and they have good reasons for doing that – reuniting the Alokozais is going to make a pretty significant dent in their territory,” one U.S. official said before Mojayed’s death, speaking on the condition of anonymity because of the sensitivity of the issue.

The most elaborate attempt on his life took place on a Saturday in mid-February, when insurgents opened fire with rocket-propelled grenades from the roof of a wedding hall that overlooks police headquarters. Two car bombs and three rickshaws exploded outside the base over the next few hours as fighters lobbed hand grenades over the concrete blast walls and U.S. soldiers and Afghan police riddled the building facade with bullets. As Mojayed’s deputy and two dozen of his men entered the wedding hall, two suicide bombers blew up inside and security forces shot a third in the head.

Voorhees, the U.S. commander at the base, estimated that dozens of people were involved in planning and carrying out the attack.

Mojayed’s brother had worried about whether he should have accepted the job.

“If it were not for serving the people, I don’t think it is a wise idea for him to come and be chief of police at this particular moment,” Mohammad said. “We’re not safe even in our homes. They can target our children, they can target our women, they can target our family members whenever they want.”

But Mojayed was undeterred.

“As the police chief of Kandahar, if I leave, what would the people do?” he asked in February. “If I escape, that means we have handed over all of Kandahar to the enemy. If I leave the battlefield, people will see no reason to fight.”

Special correspondents Habib Zahori and Javed Hamdard contributed to this report.