Charles Schwab said Tuesday that it is ending commissions for online trading in U.S. stocks, exchange-traded funds and options, the culmination of a yearslong fee battle in the brokerage industry.

Shares of Schwab fell 9.7% on fears the change will hit margins. The broker said commission fees make up 3% to 4% of net revenue each quarter. Rival brokerage firm TD Ameritrade plummeted 25.8% for its worst day in 20 years. E-Trade shares cratered 16.4% for its worst day since 2009.

Starting on Oct. 7, Schwab, which holds about $3.72 trillion in client assets, will be slashing its trading commission cost for U.S. stocks, ETFs and options from the previous $4.95 to zero. Trading options will continue to cost 65 cents per contract. The changes will apply to securities on Canadian exchanges as well.

The firm's "passion has been to make investing easier and more affordable for everyone," founder and Chairman Charles Schwab said in a press release.

"This is our price. Not a promotion. No catches. Period," added CEO Walt Bettinger.

After Silicon Valley start-up Robinhood offered stock trading for free in 2013, analysts predicted it was only a matter of time before the major brokerages were also forced to go to zero. The announcement comes after Interactive Brokers took the same step toward commission-free trades on Thursday and J.P. Morgan Chase unveiled its own free trading app in August.