The Ravens announced the news after speaking with Walker's godmother. Walker's agent, Ron Butler, also confirmed his client's death to ESPN.
"Tray was a young man with a good and kind heart," Ravens coach John Harbaugh said in a statement. "He was humble and loved everything about being part of the Ravens' team. He loved his teammates, the practice and the preparation, and that showed every day. He was coachable, did his most to improve and worked to become the best. I'll never forget that smile. He always seemed to be next to me during the national anthem; then we would give each other a big hug. May he rest in the Peace of Christ Jesus forever."
Said receiver Steve Smith Sr.: "Times like this make you hug your kids tighter. A mother lost her son today, and a family lost their brother, including us, his extended family. Tray had a bright future ahead of him outside of football and was a guy who lit up the room with his personality. I will miss seeing him every day and seeing that bright smile he always wore. I pray that his family can find peace. Rest well, Tray."
The Ravens have sent three team officials to Miami to offer their support for the family, the team confirmed to ESPN on Saturday.
Walker's agent, Ron Butler, added the Ravens have been key in the family's grieving process.
"The Ravens have been nothing but helpful," Butler said. "They're going above and beyond to make sure they are there for the family and anything the family needs. They've been in touch with me. They've been in touch with the family, and it's a first-class organization all the way around."
A public viewing for Walker is scheduled for Friday evening in Miami at Miami Northwestern High School, followed by the funeral at 1 p.m. the next day at Community Missionary Baptist Church in Miami.
"A mother lost her son today, and a family lost their brother, including us, his extended family. Tray had a bright future ahead of him outside of football and was a guy who lit up the room with his personality. I will miss seeing him every day and seeing that bright smile he always wore."Steve Smith Sr., on death of Tray Walker
Family and friend mourned Saturday at the crash site. Those who gathered at the intersection placed purple, black and yellow candles -- the colors representing the Ravens' -- to form the letters "T" and "W" around a stop sign post, as pictured in a tweet from the ABC-TV affiliate in Miami.
— Liane Morejon (@LianeMorejonTV) March 19, 2016
Walker was heading west on Northwest 75th Street on a Honda dirt bike when he collided with a Ford Escape heading south on Northwest 21st Avenue, according to the Miami-Dade Police Department. The accident occurred at about 7:50 p.m. on Thursday, and police said Walker's bike did not have headlights and that he was wearing dark clothing.
The intersection where the accident took place is a two-way stop. Walker was not wearing a helmet, Butler said.
Police said the driver of the Ford Escape stayed on the scene and was cooperating with detectives. Walker was believed to be riding the dirt bike recreationally with another NFL player, according to Butler, who said he did not know the name of that player.
Walker was treated at the Ryder Trauma Center in Miami's Jackson Memorial Hospital. Butler said earlier Friday that his client was "fighting for his life."
"There was a lot of head trauma," Butler told the Miami Herald. "The doctors tried to get the swelling down but I guess his brain went too long without oxygen."
Speaking outside the hospital, family friend Yolanda Hardy told ESPN, "That was his dream [to play in the NFL] and he made it. Tragedy struck, and we don't even have words. We don't know what to say. Just pray for the family."
Said Lissette Lowe, another family friend, "He wasn't responding to nothing they (the doctors) tried to do. They tried everything. They tried and he wasn't responding."
Earlier Friday, Harbaugh wrote an open letter to his team. In it, he wrote, "that was the kind of phone call you never want [to] get as a coach, as a parent, as a brother, as a friend. This shook me and all of us.
"There is a lot going on out there and you are going to be involved in tough and difficult situations. You are making and will continue to make important choices pretty much every day. That's okay. That's our reality. It can even be very good to be put in different circumstances. To make it right, you are going to have to grow up fast. Probably faster than many of your friends and family," he wrote, adding some messages of advice.
He ended the letter: "Remember, We are Brothers in Arms. And, again, take care of each other."
Commissioner Roger Goodell called the tragedy "a sad day for everyone in the NFL." DeMaurice Smith, the executive director of the NFLPA, said the "community of players mourns" Walker's loss.
Butler said he didn't know his client even owned a dirt bike.
"I'm really hurt by the fact that it's another young man with a promising career that lost his life on one of these bikes," the agent told the Herald.
"Don't ride it in the street. Ride it off-road. Ride it in the dirt. That's why call it a dirt bike. And wear a helmet."
A fourth-round pick of the Ravens in 2015, Walker played eight snaps on defense as a rookie, making one tackle.
He had dedicated his rookie season to his father, who died of a heart attack in 2014. The family spread Walker's father's ashes off the coast of Miami one day after Walker was drafted, his father's birthday.
Considered quiet yet good-natured, Walker endured a steep learning curve going from Texas Southern to the NFL. Baltimore made him the 16th cornerback taken in the 2015 draft, with Walker's height (6 feet 2) and length (his 33-plus-inch arms and 80⅜ wingspan were the longest known of that draft class) ideal for that position. He was expected to battle for the No. 3 or No. 4 cornerback spot on the Ravens this season.
"Tray was one of the most humble persons we brought in for a pre-draft visit," Ravens general manager Ozzie Newsome said in a statement. "That was striking. After we drafted him, he and his family were so excited to receive the call that he was about to become a Raven. It was one of the calls I will always remember. There was such joy for Tray and his family."
In mid-December, Harbaugh called Walker a "sponge" in terms of his learning.
Walker acknowledged at the end of the season that the lack of playing time -- he was inactive for half of the Ravens' games -- was frustrating.
But defensive backs coach Chris Hewitt noted the future was bright for the 2015 fourth-round pick.
"He had a vision of what he wanted to be as a player, and after last season he left our building determined that in 2016 he would be a household name in Baltimore," Hewitt said in a statement. "He had so much potential and was on his way to being a great NFL player. He will be missed and will never be forgotten."
The Ravens and some of their players also took to social media to express their condolences.
— Baltimore Ravens (@Ravens) March 18, 2016
— Steve Smith Sr (@89SteveSmith) March 18, 2016
I just heard the news.. I can't believe it. I was just with him two weeks ago. That was like my little bro. RIP Tray Walker.
— Marlon Brown (@MB_uno4) March 18, 2016
Hate we lost our brother and teammate! #ripTray #25
— CJ Mosley (@TreyDeuce32RTR) March 18, 2016
ESPN.com's Jeremy Fowler, Jamison Hensley and James Walker contributed to this report.