UPDATE: Nebraska Lt. Gov. Sheehy resigns from office - KTIV News 4 Sioux City IA: News, Weather and Sports

"Public officials are rightly held to a higher standard. We take our public trust very seriously," Nebraska Gov.. Dave Heineman said at a Saturday morning press conference where he announced Lieutenant Governor Rick Sheehy's resignation.

Sheehy resigned from office immediately following inquiries into his use of a state-issued cell phone.   An investigation by the Omaha World-Herald found that the Republican made about 2,000 late-night telephone calls to women other than his wife.  The Governor did not specify the reason for Sheehy's resignation, only saying that it had to do with his personal behavior.

Sheehy's wife Connie filed for a divorce last July after nearly 29 years of marriage.  The divorce filing stated that the marriage was "irretrievably broken."

Heineman says he plans to begin a search Monday to replace Sheehy.

"I've got a knot in my stomach, I'm deeply disappointed. I had trusted him and that trust was broken," said Heineman.

Sheehy did not appear at the press conference, and his state cell phone has been disconnected.

The 53-year-old Sheehy, a former Hastings mayor, has been considered the leading candidate to succeed Heineman in 2015.  Heineman says he would no longer support the lieutenant governor if he continued his campaign.