TD Ameritrade's Hockey Stepping Down as CEO

"Why he [is leaving] is a big mystery, as everyone liked him. He swore that TD Ameritrade would never compete with RIAs and everyone believed him. He will be missed," Welsh explained.

Hockey became president in January 2016 and CEO in October 2016. Earlier, he led TD Canada Trust for more than seven years.

In a statement, Chairman Joe Moglia said: "We are grateful to Tim for his leadership and the contributions he made to the company over his tenure as CEO. He played a key role in the successful integration of Scottrade and has taken important steps to position TD Ameritrade for long-term success."

Hockey explained: "I believe TD Ameritrade is well-positioned to continue as an industry leader and innovator, and until my last day, 100% of my energy will be focused on helping our associates drive our strategy forward. I'm intent on keeping our momentum going, and setting up my successor for long-term success."

Earlier on Monday, TD Ameritrade launched Android Auto and Echo Auto voice-activated capabilities for retail investor clients with smartphones, so they can use voice commands to track market news and account details while driving.