There had been speculation that Apple CEO Tim Cook would not be participating in an upcoming antitrust probe in the United States, but it turns out Cook will participate after all.

Kara Swisher was first to report on the update, which was confirmed by U.S. House Judiciary subcommittee chairman David Cicilline. The chairman confirmed Cook’s involvement while also confirming that other major tech chief executives would be part of the investigation as well. That includes Alphabet CEO Sundar Pichai, Amazon CEO Jeff Bezos, and Facebook CEO Mark Zuckerberg.

The hearing is scheduled to take place later this month. The subcommittee sent out letters to these CEOs back in May of this year, requesting them to take part of the investigation. Many of these executives had already agreed to take part, with Cook being one of the holdouts until now.

This probe in the United States is meant to investigate competition in digital markets, involving all four of these companies.

Apple’s antitrust issues are common knowledge at this point. The company is facing a pair of antitrust probes in the European Union right now, for instance. Apple, in particular, has earned the ire of government officials in the U.S. over its App Store policies and how they impact developers and customers. Cicilline, in particular, has described Apple’s App Store policies and fees are “highway robbery” and “exorbitant”.

It’s likely that this antitrust probe is going to take a hard look at the 30% cut Apple takes from in-app subscriptions. The subcommittee has been requesting opinions from developers who have apps available in the App Store since late in 2019. Cook will face a variety of questions, but the App Store will be a primary focus.