BOSTON — Odin Lloyd did not own a car, so, just after dawn, he would pedal his bicycle from his Fayston Street home past blocks checkered with overgrown yards and rusted fences in one of Boston’s roughest neighborhoods.

Mr. Lloyd, 27, would be on his way to work as a landscaper, or sometimes to an odd job when he could find one. A gifted high school athlete, he had not abandoned his childhood dream of playing pro football. He played with a semipro team, the Boston Bandits, sometimes on high school fields — even if he could not always afford the $75 dues.

Forty-five miles away in the suburbs, Aaron Hernandez lived in a four-story mansion with an in-ground pool. A former college and high school football all-American, he drove a $75,000 car and played tight end for the New England Patriots before sellout crowds. Last year, when he was just 22, he signed a $40 million contract extension.

Mr. Lloyd and Mr. Hernandez had virtually nothing in common, other than a love for football. But their lives did cross, and now Mr. Hernandez is in jail, charged with Mr. Lloyd’s murder.

Interviews with more than a dozen friends and relatives of both men reveal a complicated relationship that offered Mr. Lloyd a glimpse of a rarefied corner of professional sports, but was also filled with constant reminders of the vast gulf between the two athletes.

Mr. Lloyd’s murder and the subsequent revelation that Mr. Hernandez is being investigated in a separate double homicide have tarnished the Patriots organization, which holds itself up as a model franchise, and delivered the latest black eye for the National Football League, a league that has long coped with players who commit violent crimes.

But on Fayston Street, where Mr. Lloyd lived, and in Bristol, Conn., where Mr. Hernandez grew up, the murder and its fallout have come as shocking, and tragic, mysteries.

Mr. Hernandez and Mr. Lloyd might never have met but for two sisters from Bristol. Mr. Hernandez and one of the sisters, Shayanna Jenkins, were high school sweethearts. Last year, when she became pregnant with his daughter, he bought a sprawling house in North Attleborough, Mass. Their daughter was born in November, and Mr. Hernandez began calling Ms. Jenkins his fiancée.

Sometime in the last 18 months, Mr. Lloyd began dating Ms. Jenkins’s sister, Shaneah. At Jenkins family gatherings, the men became acquainted. Mr. Lloyd, of course, knew all about Mr. Hernandez’s football career. But Mr. Lloyd did not discuss the Boston Bandits with Mr. Hernandez, at least at first.

“When they first started dating, I asked Odin, ‘Does he know that you play football?’ ” said Cliff Anderson, a player on the Bandits. “He goes, ‘No, I didn’t mention it to him; there’s no need for me to mention it.’

“He didn’t want to make it like he was a groupie, that he was trying to use him in any way.”

Over time, Mr. Lloyd and Mr. Hernandez started spending time together away from the Jenkins sisters. They arranged their own outings, and Mr. Hernandez’s towering presence — he is 6 feet 2 inches and 250 pounds — and his expensive cars were spotted in Mr. Lloyd’s rough Dorchester neighborhood.

Mr. Lloyd, his friends said, was the kind of football player who danced onto the field, took command of the huddle and always had his teammates’ backs during games. Born in St. Croix, he spent a few years in Antigua and was raised in Dorchester. At 5-11 and a sturdy 215 pounds, he was a hard-hitting linebacker. He attended John D. O’Bryant School of Mathematics and Science, and in 2003 the previously downtrodden football team contended for the league championship, in part because of his energy.

“He was my best hitter on the team that year,” his coach Jeff Venter said. “He was pretty much feared.”

Mr. Venter said he thought Mr. Lloyd had the skills to play Division I football. But his grades were too poor for him to be a prospect, and they even caused him to miss much of his senior season. Mr. Venter called the loss “heartbreaking.”

When Mr. Lloyd graduated in 2005, he was admitted to Delaware State University but never attended classes, apparently because of financial problems, according to one of his uncles.

Football, however, remained a constant. He joined the Bandits, who play home games in front of fans who pay $6 for a seat, with children admitted free. Mr. Lloyd seemed to thrive in the low-profile world of semipro football.

“He didn’t care about material things or what other people thought of him,” said Kerome Coley, a friend. “That’s why so many people gravitated to him.”

Another teammate, Dee Hodge, said Mr. Lloyd knew his big-time pro football dreams would never materialize.

“We don’t have no agent,” Mr. Hodge said. “Nobody is calling us or nothing. We are in a grown-man Pop Warner league.”

But Mr. Hernandez, the star tight end featured on ESPN highlights, offered a unique chance to touch the glittering stage of professional football. “You were there with someone who is in ‘The League,’ ” Mr. Coley said. “You see him on TV. You admire this person.”

A Football Family

In 2005, the year Mr. Lloyd graduated from high school, Mr. Hernandez eclipsed the lofty athletic legacies of both his father and older brother. In Bristol, his father, Dennis, had earned the nickname the King when he lettered in three sports at Bristol Central High School in the early 1970s. Dennis Hernandez went on to play at the University of Connecticut, as did Aaron’s older brother, D. J.

As a high school sophomore, Aaron Hernandez kept with family tradition and verbally committed to UConn. But in his junior year, he set state records for receiving yards and touchdowns and posted eye-catching statistics, like 376 receiving yards in one game. College coaches from the around the country came to Bristol, a hardscrabble city of 60,000 once known for its clock making but now better known as the home of ESPN.

Mr. Hernandez switched his commitment to the University of Florida, after visiting the campus and staying with Tim Tebow, then the Gators’ star quarterback. The decision shocked people in Bristol, but by then most had seen a change in Mr. Hernandez. His father, Dennis, had died in January 2006, just after Aaron’s junior season at Bristol Central.

The death ended epic backyard football games, and Aaron, the youngest son, appeared to withdraw into himself.

“Everyone in town knew Aaron, and he was a cool kid that made you feel good,” said Andrew Malak, 18, a relative of the family. “He was still nice after that, but just quieter.”

In a 2009 interview with USA Today, Aaron’s mother, Terri, recalled the effect her husband’s death had on Aaron: “It was a rough process, and I didn’t know what to do for him. He would rebel. It was very, very hard, and he was very, very angry. He wasn’t the same kid, the way he spoke to me.”

Mr. Hernandez began hanging around with a tougher crowd. He graduated early from Bristol Central — he was only 17 — so he could enroll at Florida and prepare for his college football life.

But trouble followed him to Florida.

During his freshman year, before he turned 18, Mr. Hernandez was arrested after a fight with a bouncer at a bar. He received deferred prosecution after being charged as a juvenile. In the fall of that year, The Orlando Sentinel reported that Mr. Hernandez was questioned by police about a shooting that injured two men. Friends from Connecticut were with Mr. Hernandez that night, the Sentinel reported.

And as a sophomore, he was suspended for the season-opening game, apparently because of a positive test for marijuana, Mr. Hernandez later acknowledged.

By his junior year, Coach Urban Meyer was saying that Mr. Hernandez had been rehabilitated with daily Bible study sessions that the coach conducted personally.

But N.F.L. teams were unconvinced when Mr. Hernandez turned pro, skipping his senior season. A first-round talent, he was drafted by the Patriots in the fourth round, and even that was viewed as a risky move given Mr. Hernandez’s track record. There were reports that he had failed multiple drug tests.

Still, Mr. Hernandez was embraced by Bristol as a hometown hero. Many city residents made pilgrimages to watch him play for the Patriots.

This week, many of those residents could not reconcile the Aaron Hernandez they knew as a youngster and the one they have seen this week in handcuffs.

“It looks like he just fell in with the wrong crowd,” Mr. Malak said.

But even that is not enough of an explanation for those in Bristol who thought they knew Mr. Hernandez best. They say they do not recognize the young man who took a picture of himself with a handgun when he was a college student at the University of Florida. They say they can’t understand how Hernandez can be sitting in jail, charged with murder.

“I guess you never know anyone,” said Jerry Coyne, whose son Matt was the quarterback on Mr. Hernandez’s high school team.

A Trip in a Rented Car

On the Saturday night before he was found dead, Mr. Lloyd drove to a Bandits scrimmage in a Chevy Suburban that belonged to Mr. Hernandez, with whom he had been partying at a club a night earlier. Mr. Lloyd usually bummed rides from teammates to practices. This time, he pulled up next to Mike Branch, a Bandits coach who had also coached him in high school.

Mr. Branch wanted to know whose car it was, because, as he said Thursday, “I knew he didn’t have no Suburban.”

Mr. Lloyd answered succinctly: “You know whose car it is, coach.”

A little more than a day later, in the early morning hours of June 17, Mr. Hernandez and two friends rolled up to Mr. Lloyd’s home, this time in a rented silver Nissan Altima.

At 2:29 a.m., according to prosecutors, Mr. Hernandez texted Mr. Lloyd, saying, “We’re here.” As Mr. Lloyd left the house, his sister casually glanced out the window at the Altima. But this was not a prelude to another visit to an after-hours nightclub. Mr. Hernandez, prosecutors say, was angry with some of the people Mr. Lloyd had talked with at the club Friday night. Irritated, he talked about how he could no longer trust Mr. Lloyd. Roughly 40 minutes later, apparently worried about Mr. Hernandez’s intentions, Mr. Lloyd texted his sister from the Altima.

“Did you see who I was with?” he asked. There was a pause of a few minutes; his sister’s phone had lost its charge.

“Who?” she finally replied.

“NFL,” Mr. Lloyd texted back, then added, “Just so you know.”

Odin Lloyd was not referring to his childhood dream. He was identifying the big-time football star he had once gravitated toward but now feared.

Mr. Lloyd’s text was sent at 3:22 a.m. Prosecutors said surveillance video from businesses in the industrial park where Lloyd’s bullet-riddled body was found showed the Altima heading for a undeveloped section of the industrial park at 3:25 a.m. Shortly after, night shift workers in the park heard multiple gunshots.

At 3:27, the Altima was visible again leaving the secluded area. Two minutes later, prosecutors said, Mr. Hernandez was seen parking the Altima in his driveway less than a mile away and stepping out of the vehicle, pistol in hand.

Mr. Hernandez has pleaded not guilty to all charges. His lawyers Thursday said they looked forward to testing the quality of the prosecution’s evidence, which they described as a “theory.”

Interviewed outside her Fayston Street home on Friday, Mr. Lloyd’s mother, Ursula Ward, said: “I just want my son back. I just want him to be able to rest in peace.”

Steve Eder contributed reporting from New York; Ben Shpigel from Boston; and Joe Drape from Bristol, Conn.