BOSTON (CNN) - An investment group headed by three self-described "lifelong fans" has reached an agreement to acquire the NBA's Boston Celtics, one of the most storied franchises in professional sports, for $360 million.

"Our goal as an ownership group is to raise more championship banners," said Wycliffe Grousbeck, a co-managing partner of the group. "We love this team, we value our fellow fans and we are excited about the opportunity to be involved with the team's future."

"It's been a great franchise with great tradition. We became very attracted to the franchise because of that great tradition and because all it's done for the Boston area," said Steve Pagliuca, another co-managing partner.

The Celtics, who have won 16 NBA championships, are one of the few professional sports franchises that are publicly owned, traded on the New York Stock Exchange. A majority of the stock is controlled by the Gaston family.

Paul Gaston, whose father bought the team in 1983, said that after nearly two decades of ownership, "Things change in life, and it's time for us to move on."

He added, "We have mixed emotions. It's been a huge part of our lives. And it's not something that's ever going to be replaced."

In addition to Grousbeck and Pagliuca, who are principals with venture capitalist firms, the third co-managing partner will be Grousbeck's father Irving, co-founder of Continental Cablevision. More Boston-area investors are expected to become part of the group, Pagliuca said.

"We'll be choosing investors who will really strengthen the group," he said.

The sales price is reportedly more than 20 times as much as the amount the Gaston family paid in 1983. According to the Boston Globe, the sales price back then was between $15 million and $18 million.

The Celtics are one of the few publicly-traded stand-alone teams in sport. The Boston Celtics Limited Partnership (BOS: Research, Estimates) owned 48 percent of the team as its only operation.

Shares in the generally thinly traded were generally held in small numbers by individuals, most of them Celtics fans. There were only 13 institutional shareholders of the shares.

About 200 shares traded Friday before the announcement, closing at $11.35, up 75 cents. The buyers of the team did not assume $50 million in debt as part of the purchase price, and the 48 percent interest in the remaining $310 million purchase price comes to about $55 a share. But exact cash distribution to partnership shareholders has yet to be determined and will be based on other assets and liabilities as well after the close.