Weaver made both announcements during a news conference, as well as a three-year contract extension for general manager Gene Smith. NFL Network insider Jason La Canfora first reported the move to dismiss Del Rio, who informed his coaching staff of the decision on Tuesday, according to a team source.
The Jaguars also confirmed a report by NFL Network's Albert Breer that defensive coordinator Mel Tucker will take over as interim head coach. Tucker joined the Jaguars in 2009 following four seasons as an assistant with the Cleveland Browns.
Weaver said Kahn was not involved in the decision to fire Del Rio, but that the decision on who would replace him will likely be a "joint effort" between the two men.
"I think I'll play a major role in influencing that decision based on conversations that Shahid and I have had," Weaver said. "He trusts my experience."
Weaver said the unusually active day was "bittersweet."
"I told Jack that I appreciated the nine years that he served the team, but I told Jack that we deserved better," Weaver said. "We've been very average over the last couple of years."
Hired by the Jaguars in 2003, Del Rio finishes his career in Jacksonville with a 69-73 overall record, including a 1-2 mark in the postseason. His team hasn't made the playoffs since 2007, when Jacksonville finished 11-5 and qualified as a wild card. The Jaguars didn't win the AFC South in any of his nine seasons.
Del Rio said he respects Weaver's decision.
"Theres a Little bit of unfinished business, which is that I didn't get to take this team to a championship, which was the goal," Del Rio said while speaking to reporters outside his home on Tuesday.
The second head coach in team history, Del Rio's job security had been tenuous since Weaver said the coach needed to make the playoffs this year to secure a 10th season in Jacksonville. The Jaguars won their opener against the Tennessee Titans then lost their next five. They were essentially eliminated from the postseason with Sunday's 20-13 loss to Houston.
"Any time the owner makes a statement with 'you better make the playoffs, or else,' and you start the year the way we started, it's tough," Del Rio said.
Weaver considered firing Del Rio after last season, but kept him partly because of the uncertainty surrounding the NFL lockout. Weaver refused to give contract extensions to any of Del Rio's assistants, putting everyone on alert that this was a win-or-else season.
Weaver said Tuesday he wanted to announce both moves -- Del Rio's firing and the sale of the team -- at the same time, hoping to avoid an awkward situation.
The Associated Press contributed to this report.