Tesla Inc founder Elon Musk apologized to British caver Vern Unsworth for comments he made about him following the rescue of a dozen Thai schoolboys and their football coach from a cave in northern Thailand.

“His actions against me do not justify my actions against him, and for that I apologize to Mr. Unsworth and to the companies I represent as leader,” Musk said in a tweet. “The fault is mine and mine alone.”

Unsworth, who played a leading role in the rescue, said on Tuesday that he has been approached by British and American lawyers and will seek legal advice after Musk directed abuse at him on Twitter.