He presided behind the counter of a storefront New Jersey fried chicken restaurant, making his home with his family in an apartment above it. To some of his friends, Ahmad Khan Rahami was known as Mad, an abridgment of his name rather than a suggestion of his manner, and they liked that he gave them free food when they were short on money.

Beyond that, his other known obsession was souped-up Honda Civics that he liked to race. In recent years, though, some friends noticed a marked change in his personality and religious devotion after what they believed was a trip to Afghanistan, where he and his relatives are from.

In fact, a federal official, speaking on the condition of anonymity, said Rahami had actually traveled to Pakistan, for three months in 2011 and, most recently, to Quetta, for nearly a year, where he stayed with family, returning to the United States in March 2014.

Back home in New Jersey, he and his relatives had a fractious relationship with neighbors and the police in Elizabeth, N.J., because of the always-open hours of their restaurant and the rackety customers it attracted. The long-standing friction led to the Rahami family’s filing a federal lawsuit in 2011 against the city and its Police Department in which they alleged that they were harassed and intimidated because of their religion. In the suit, they accused a local businessman of complaining to them, “Muslims make too much trouble in this country.”

Now, Rahami is suspected of being responsible for the bombings over the weekend in both New York and New Jersey. He was taken into custody on Monday after being discovered asleep in a bar doorway in New Jersey and then wounded in a gunbattle with the police.

A 28-year-old naturalized citizen, Rahami lived in Elizabeth, about 15 miles from New York, above First American Fried Chicken, a family business apparently owned by his father, Mohammad. Several brothers may also have worked there.

Ahmad Rahami was born on Jan. 23, 1988, in Afghanistan and came to the United States as a child. Neighbors said they believed that he was one of at least a half-dozen siblings, though like much about his life, the exact number was unclear.

Flee Jones, 27, grew up with Rahami, and when they were young played basketball with him in the local park. As an adult, Jones, a rapper, was a regular at the chicken place, where the food was plain but cheap. He said the Rahamis would let him and his friends host rap battles in the back of the restaurant.

“It was nothing but good vibes,” said Jones, who helped write a song called “Chicken Joint” as an informal advertisement for the restaurant.

At this point, little is known of Rahami’s ideology or politics, or whether he has any connections to foreign terrorist organizations. He used to wear Western-style clothing, and customers said he gave little indication of his heritage.

Around four years ago, though, Rahami disappeared for a while. Jones said one of the younger Rahami brothers told him that he had gone to Afghanistan. When he returned, some patrons noticed a certain transformation. He grew a beard and exchanged his typical wardrobe of T-shirts and sweatpants for traditional Muslim robes. He began to pray in the back of the store.

His previous genial bearing turned more stern.

“It’s like he was a completely different person,” Jones said. “He got serious and completely closed off.”

Andre Almeida, 24, who lives nearby and eats at the chicken restaurant once or twice each week, said he found the change quite striking but was hesitant to reach any conclusions.

Rahami kept little social media presence that law enforcement has been able to locate.

“He’s a little bit of a wraith, a ghost,” a law enforcement official said.

There is no evidence yet that Rahami received any military training abroad, the federal official said, but investigators remain intent on learning more about his time overseas.

“Where did he really go and what did he do overseas that a kid who lived a normal New Jersey life came back as a sophisticated bomb-maker and terrorist?” the official said.

Much about his New Jersey life did seem unremarkable. Amarjit Singh, a limousine driver, was friends with Rahami at Edison High School. The person he knew, he said, was a determined student with an abundance of friends and a string of girlfriends. “Everyone seemed to like him,” he said. “Smart, funny, humble, never did anyone harm.”

He viewed the teenage Rahami as the prototypical immigrant, teetering between two worlds. While he wore jeans and sweatshirts like his friends, he preferred Afghan music and prayed at the mosque on Friday. Collisions between those worlds sometimes led to rifts with his father, who was more religious and traditional than he was.

“The two of them would argue,” Singh said. “There seemed to be a lot of tension.”

His father was especially displeased when Ahmad Rahami had a daughter out of wedlock.

After high school, Singh said that he and Rahami had worked together for a while on the night shift at Royal Fried Chicken in Newark. Singh worked the fryer in the back. Rahami handled the register. Whenever Singh got into a dispute with unhappy customers, he remembered Rahami stepping in as the peacemaker.

In recent years, the two drifted apart. Singh was also aware that Rahami had traveled abroad and that he had become more religious and had taken to wearing Muslim robes.

The events on Monday were not Rahami’s first encounter with law enforcement. He was arrested in 2014 on weapons and aggravated assault charges for allegedly stabbing a relative in the leg in a domestic incident, according to court documents. He spent over three months in the Union County Jail on the charges, according to a high-ranking law enforcement official with knowledge of the investigation. A grand jury, however, declined to indict Rahami. He also spent a day in jail in February 2012 for allegedly violating a restraining order and another day in October 2008 for unpaid traffic tickets, the official said.

In 2005, Rahami’s father filed for bankruptcy, saying in court documents that he had just $100 in the bank and $38,609 in debt, mostly from credit cards. He said he was separated and had eight dependent children.

The family, as it ran its chicken restaurant, developed a tense relationship with the community, though it drew a horde of loyal patrons who appreciated their cheese fries and friendly service.

When the restaurant opened about a decade ago, Rahami’s father, Mohammad, was always the one behind the counter, said Ryan McCann, 33, a frequent patron who lives in Elizabeth. Increasingly, his son Ahmad replaced him. Recently, only Ahmad Rahami ran the place.

At first, the restaurant was open 24 hours a day and after a while became a local nuisance, said J. Christian Bollwage, the mayor of Elizabeth and a neighbor. Rowdy crowds appeared after midnight.

Dean McDermott, who lives nearby and is a news videographer, complained, as did others. Often McDermott discovered patrons loitering in his yard and urinating in his driveway, and he called the police.

In response to the persistent complaints, the chicken restaurant was given a series of summonses for violating an ordinance that compels certain retailers to close at 10 p.m.

But the Rahamis flouted the requirement, contending they were exempt from it, and neighbors continued to contact the police. In June 2010, two of Ahmad Rahami’s brothers, Mohammad K. and Mohammad Q., were arrested after an altercation with police officers who had shown up after 10 to tell them to close down for the night. Mohammad Q., a minor at the time, was not charged, while Mohammad K. eventually pleaded guilty to preventing a police officer from making an arrest and paid a $100 fine.

In 2011, Rahami’s father and those two sons filed a federal lawsuit against the City of Elizabeth, the Police Department, nine police officers, McDermott and others. In the lawsuit, the Rahamis alleged that the family was the target of a campaign of humiliation and retaliation.

In the complaint, the Rahamis said McDermott told them that “Muslims make too much trouble in this country” and “Muslims should not have businesses here.”

The mayor said: “It was neighbor complaints; it had nothing to do with his ethnicity or religion. It had to do with noise and people congregating on the streets.”

Among the court filings in the case was a letter from the family’s lawyer that said the elder Rahami was traveling in Pakistan in July 2011. Another letter, dated Sept. 16, 2011, said that Mohammad Rahami had been hospitalized and that his family was in Afghanistan “but returning over the next few days.”

The suit has yet to be resolved. McDermott said a fragile and informal truce was reached, whereby the restaurant would close at midnight or 1 a.m.

A few months ago, however, a for-sale sign appeared in the front window. It is still there.

Some of Ahmad Rahami’s customers were fond of him, especially those he favored with free meals. “He gave me free chicken,” said Ryan McCann. “He was always the most friendly man you ever met.”

Other customers, however, found him and his relatives off-putting. “They seemed secretive, a little mysterious,” said Jessica Casanova, 23, another neighbor. “They’re too serious all the time.”

Another neighbor, Joshua Sanchez, 24, was also struck by the familial insularity inside the chicken restaurant he referred to as “the shack.”

McCann, however, said Ahmad Rahami was obsessed with cars, particularly Honda Civics that were custom-built to race.

“He always talked about fast Honda Civics, about how he loved them,” McCann said.

McCann said he last ate at the restaurant two weeks ago. “He was having a conversation about his cars,” McCann said. “How he likes to soup them up and race them.”

At 10:30 on Sunday night, the bombs having gone off and the hunt for the perpetrator well underway, Junior Robinson, 19, stopped in at First American Fried Chicken for some drumsticks and fries. Though the place was normally busy at that hour, he was the only customer. Mohammad Rahami served him.

Ahmad Rahami was not there. Robinson gave that no thought.

© 2016 The New York Times Company