Private-equity firm Veritas Capital and Elliott Management Corp. will acquire athenahealth Inc. for $135 per share, ending a months-long, sometimes-contentious process to push the health records company into a sale.

The all-cash transaction values athenahealth at about $5.7 billion, the firms said in a statement announcing the transaction Monday. The price is a 12 percent premium to where the shares closed on Friday.

Athenahealth rose 9.2 percent to $131.45 at 9:04 a.m. in New York, before the market opened.

Jonathan Bush, nephew of former President George H.W. Bush, co-founded athenahealth in 1997 as a cloud-based alternative to software systems used by medical offices for billing. The company opened offices in Belfast in 2008 and is now among the largest employers in Waldo County with about 950 workers.

After the deal closes, athenahealth will be combined with Virence Health, Veritas’s health-care services company, the firms said. Virence offers hospitals and physician practices services to manage their revenue and workflow. The combined company will keep the athenahealth name, and will be led by Virence Chief Executive Officer Bob Segert.

Although the company’s Belfast office was closed Monday for the federal holiday, two employees who wished to remain anonymous told the Republican Journal that talk of the impending sale was creating a lot of uncertainty. One worker said there was noticeable tension after the company pushed back its third-quarter earnings call earlier this month. The call, which was rescheduled for Nov. 12, was canceled with Monday’s announcement of the sale.

The other worker raised the question of redundancies at Virence and athenahealth, and how those would be handled by the new owner.

The sale was pushed by Elliott, the sometimes-activist fund run by billionaire Paul Singer. Earlier this year, New York-based Elliott went public with a 9 percent stake in Athenahealth, and said it was prepared to offer $160 per share for the company, subject to due diligence. Elliott said that the company, which provides online business services including billing for health-care providers, had been mismanaged and failed to grow as much as it should have.

Athenahealth refused Elliott’s proposal. The company has been formally exploring a sale since June, when Chief Executive Officer Jonathan Bush stepped down following allegations of misconduct.

“Operating as a private company with Veritas’s ownership and support will provide athenahealth with increased flexibility to achieve our purpose of unleashing our collective potential to transform health care,” said Jeff Immelt, the former General Electric Co. CEO who has been Athenahealth’s executive chairman.

Elliott’s private equity arm, Evergreen Coast Capital, will keep a minority stake in the new company. The deal is expected to close in the first quarter of 2019, the firms said.

Ethan Andrews of the Republican Journal contributed to this report.