BOSTON -- Former NFL star Aaron Hernandez, who was serving a life sentence for a murder conviction and just days ago was acquitted of double murder, died after hanging himself in his prison cell early Wednesday, Massachusetts prisons officials said.

Guards found Hernandez unresponsive in his cell at the Souza-Baranowski Correctional Center in Shirley just after 3 a.m., Department of Correction spokesman Christopher Fallon said in a statement.

The former New England Patriots tight end was pronounced dead at UMass Memorial-HealthAlliance Hospital in Leominster about an hour later. He was 27.

Hernandez was in a single cell in a general population housing unit in the maximum-security state prison. He hanged himself using a bed sheet that he attached to a cell window, Fallon said.

Hernandez tried to block the cell door from the inside by jamming the door with various items, Fallon said.

Law enforcement sources told ABC News that Hernandez was found with "John 3:16" written across his forehead. That Bible verse reads, "For God so loved the world that he gave his only begotten son, that whosoever believeth in him should not perish, but have everlasting life."

Fallon said he was not aware of any suicide note written by Hernandez and stressed that an investigation is ongoing. He said officials had no concern that Hernandez was planning on taking his own life. He also noted that if there was a concern about his well-being, Hernandez would have been transferred to a mental health unit.

"The family and legal team is shocked and surprised at the news of Aaron's death," Hernandez's lawyer Jose Baez said in a statement. "There were no conversations or correspondence from Aaron to his family or legal team that would have indicated anything like this was possible. Aaron was looking forward to an opportunity for a second chance to prove his innocence. Those who love and care about him are heartbroken and determined to find the truth surrounding his untimely death. We request that authorities conduct a transparent and thorough investigation.

"The Baez Law Firm will participate in its own examination into this tragic event and update the media and public on its findings when they become available."

Massachusetts prisons officials say former NFL star Aaron Hernandez hanged himself in his cell and was pronounced dead at a hospital. He was 27. AP Photo/Steven Senne

Hernandez's former agent, Brian Murphy, said Wednesday morning there was "absolutely no chance" Hernandez took his own life.

"Chico was not a saint, but my family and I loved him, and he would never take his own life," Murphy said.

That sentiment was shared by Hernandez's cousin, Randy Garcia.

"Most of us are in shock. We still don't believe that this happened," Garcia told WTNH via Skype. "We still think there's no way Aaron would take his own life."

Hernandez was moved to tears on Friday after he was acquitted of the 2012 fatal shootings of Daniel de Abreu and Safiro Furtado in Boston. Just before his acquittal, Hernandez was seen blowing kisses to the little girl he fathered with fiancée Shayanna Jenkins-Hernandez. Cameras captured the tender exchange.

Hernandez was still serving a life sentence without the possibility of parole for his conviction in the 2013 shooting of Odin Lloyd, a semiprofessional football player who was dating Jenkins-Hernandez's sister.

Garcia said one of his nephews posted on Facebook that he had spoken with Hernandez on Tuesday night and that "he was in good spirits, that he was -- his conversation was nothing but joy -- that he was thinking about his future and how he was going to win his appeal in his Odin Lloyd case, and he was in really good spirits. So for this to happen -- we're shocked and we still don't believe that he took his life, and we still believe there's a lot of foul play going on."

According to ESPN's Roger Cossack, Hernandez's legal team can file a motion to vacate his conviction for the murder of Lloyd. Martin W. Healy, the chief legal counsel to the Massachusetts Bar Association, told The Boston Globe that the legal rule is called abatement ab initio. Healy said that upon a person's death, if he or she has not exhausted the legal appeals, the case reverts to its status at the beginning; it is as if the trial and conviction never happened.

A lawyer who represents Lloyd's mother says she's moving forward with a wrongful-death lawsuit against Hernandez's estate. He says he has placed liens on Hernandez's Massachusetts home, estimated to be worth $1.3 million.

Hernandez was tried but acquitted in the slayings of de Abreu and Furtado, whom prosecutors contended were gunned down after one of the men accidentally spilled a drink on Hernandez in a Boston nightclub. The jury in that case found Hernandez not guilty of first-degree murder but convicted him of unlawful possession of a gun, and the judge sentenced him to an additional four to five years in prison -- separate from his existing life sentence.

His death was "a shocking and sad end to a very tragic series of events that has negatively impacted a number of families,'' said Bristol County District Attorney Thomas Quinn, who prosecuted Hernandez in the Lloyd case.

Ernesto Abreu, the father of one of the men Hernandez was acquitted of killing, told the Boston Globe, "I'm not happy about his death. It's actually a shame. Any loss of life is a shame. I believe in leaving things in God's hands."

Hernandez's death came on the same day the Patriots visited the White House to mark their Super Bowl LI win.

The Patriots didn't comment Wednesday, with a spokesman issuing this statement in the morning: "We are aware of the reports, but I don't anticipate that we will be commenting today."

A star at the University of Florida who dropped to the fourth round of the NFL draft because of misbehavior in college, Hernandez was a productive tight end for the Patriots for three seasons.

One of Hernandez's former college teammates, Dolphins center Mike Pouncey, posted on Instagram about the news.

To my friend my brother! Through thick and thin right or wrong we never left each other's side. Today my heart hurts as I got the worse news I could have imagined. It was just a day ago we shared our last convo. I will forever miss you and love you bro. we will meet again rest easy! ❤️🙏🏽 A post shared by Mike Pouncey (@mikepouncey) on Apr 19, 2017 at 5:11am PDT

Pouncey's brother Maurkice also posted on Instagram, as did Hernandez's former Florida teammate Joe Haden.

Dan Gronkowski, Hernandez's former teammate with the Patriots and the brother of current Patriots tight end Rob Gronkowski, called the news "sad."

"When I was on the team with [Aaron Hernandez], it was Rob [Gronkowski], myself and [him]. We all got along and had a good time. We didn't have any issues with Aaron, ever," he told ESPN's Josina Anderson. "So I mean that was all just a side thing that no one knew what was going on. We didn't even know that that was even happening. It wasn't even like we thought something like that was going on. So, it's just sad to hear that, knowing that you [knew] somebody that has gone through that stuff and chose that route."

Hernandez grew up in Connecticut and played for the Patriots from 2010 to 2012.

During his second year with New England, he caught 79 passes for 910 yards and seven touchdowns and helped the team reach the Super Bowl. In 2012, he signed a five-year, $40 million contract extension.

The team released him in June 2013, shortly after he was arrested in Lloyd's killing.

The Associated Press contributed to this report.