Heidel revealed the news via Schalke's official Twitter account:
He added Goretzka, 22, has completed a medical with the German champions and signed a contract, as Schalke's Twitter account relayed:
"We were very sorry to hear this. [Bayern CEO] Karl-Heinz Rummenigge told us yesterday that Leon has completed a medical. We are losing a very, very good player. He has signed a contract with Bayern from the 1st July 2018.
"We did everything we could to try and keep him. In summer he and his agent reached an agreement, but he wanted time to develop. We can cope with this situation, it wasn't a complete surprise. We are prepared for this."
It is little surprise, especially given his contract situation, that a number of Europe's top clubs were pursuing him, as he is a high-quality player.
An accomplished box-to-box midfielder, Goretzka boasts a composure and authority that belies his relative youth.
Per Squawka, he contributes in defence and attack and should be a fine addition to an impressive Bayern squad:
It is a big blow for Schalke that he has opted to depart, especially as they will receive no fee for him.
Goretzka joined the club from VfL Bochum for between €3 million and €4 million in 2013 and has made 101 appearances for Schalke in the Bundesliga.