The former chief operating officer of Martin Shkreli's hedge fund firm testified Friday that he filed a Securities and Exchange Commission complaint against Shkreli while still working for the "pharma bro" in May 2012.

The executive, Jackson Su, said he was spurred to make that complaint on the SEC's website because he believed "there was no transparency in the amount of assets" that Shkreli's MSMB hedge funds had, and in how those assets were being described to investors.

"There was variation in the assets under management that were verbally thrown around without any consistency, and that was a red flag for me," Su testified in Brooklyn, New York, federal court at Shkreli's securities fraud trial.

Su, 42, said he was interviewed by an SEC investigator about his complaint in June 2012.

But Su remained at the hedge fund firm until December 2012, he testified.

"The last day I was there, Martin took $10,000 from what was left in the bank account" for Retrophin, the drug company Shkreli was founding, Su testified.

At that time, before Shkreli took the money, Su said, Retrophin's account contained just $20,000.

"And that was the last straw for me," Su said.

Su said that as he packed his bag, MSMB President Tom Fernandez saw that he was distraught, and walked him out of the offices.

Su said he told Fernandez, "I'm not going back to work, all these things don't add up ... and I was done."

Su testified, "I got really tired of all the things I saw going on in the company."

Those things included one incident in the summer of 2012 that Su said left him "surprised and taken aback."

Su said that in August of that year, Shkreli dropped off to him a promissory note that indicated MSMB Healthcare, one of his hedge funds, had loaned $900,000 to Retrophin at 12 percent annual interest, to be repaid at the end of 2012.