Uber's Kalanick was in Chicago to interview a COO candidate when he got the letter demanding his resignation

When Uber CEO Travis Kalanick received a letter from investors demanding his resignation Tuesday night, he was in Chicago to interview a candidate for the company's open chief operating officer position, according to the Wall Street Journal.

Ironically, part of the reason investors urged Kalanick to step aside was few potential candidates wanted to take the COO job if he stayed on as CEO, the Journal reported.

Uber has been searching for a COO since early March. At the time, amid accusations of pervasive sexism at the company and the departure of several top executives, Kalanick announced he was "searching for a partner" to help him run Uber.

Since Uber began the search for a COO, "several" potential candidates declined the job, the Journal reported. And at least some board members were growing frustrated with the pace of the search, according to the Journal.

That Kalanick was on company business when he got the letter demanding his resignation is somewhat surprising. He announced last week he would be taking a leave of absence from the company.

Kalanick resigned as CEO late Tuesday night PT. His departure follows a series of scandals and controversies in the first half of 2017, including allegations of a toxic company culture.

Read the full report here.