Elon Musk called a British cave explorer a pedophile after the man criticized Musk’s effort to help in the rescue of a Thai soccer team as a publicity stunt.

Musk’s now-deleted post on Twitter adds to a long list of controversial tweets by the Tesla Inc. (TSLA.O) chairman and founder. He’s used the social network to promote his companies, spar with short sellers who are betting against Tesla shares and needle journalists who question the businesses’ prospects. Musk has 22.3 million followers on Twitter.

The billionaire offered a “kid-size submarine” to help rescue the boys and their coach after they became trapped in a cave in northern Thailand. A Thai official said the equipment, built by Musk’s rocket company, Space Exploration Technologies Corp., wasn’t practical. Musk travelled to the site in Chiang Rai province, but the team was rescued by Thai divers with aid from an international group of volunteers.

British diver Vern Unsworth, a volunteer who played a key role in organizing the rescue, said in an interview Friday with CNN that the submarine was “a PR stunt.” He said Musk could “stick his submarine where it hurts,” and that it had “absolutely no chance of working.”

Over the weekend, Musk fired back in a series of tweets, without specifically naming Unsworth. The Tesla boss said he hadn’t seen “this British expat guy” in the caves during the rescue, only Thai military divers. Musk also said he would make a video to prove that the mini-sub could have helped in the rescue. “Sorry pedo guy, you really did ask for it,” he wrote.