Amazon has shaken shareholders of online residential real estate services.

Having disrupted the brick-and-mortar market with its physical bookstores and drive-up convenience stores, in addition to rattling the grocery delivery business with its $13.7B Whole Foods Market deal, the e-commerce behemoth is looking into entering the residential referral business.

That is what experts have inferred from the new “Hire A Realtor” placeholder web page on Amazon’s website, GeekWire reports. The page allows users to input a ZIP code to search for a broker near them and has a “Coming Soon” note, signaling an expansion into real estate referrals.

The expansion would challenge online marketplace companies like Zillow, Redfin and Realtor.com, which allow users to list and search home prices and houses available for sale and rent on the market. The news sent Zillow’s stock falling July 12 almost 4% to $44.54/share as anxiety hit investors.

Experts speculate this move could be a part of Amazon’s broader push to form its own service-provider business, similar to Best Buy’s “Geek Squad.” The company is already hiring smart-home experts to provide consultations and installations for customers, Recode reports. Its army of gadget specialists has been unveiled in seven markets and is quietly growing. These experts provide services such as free Alexa consults and in-home product installation.