Amid promises from Twitter to improve the “health” and crackdown on “hate speech” on the social media platform, millions of Twitter users received racist and vulgar tweets from Twitter CEO Jack Dorsey Friday after his account was hacked.

“Hitler is innocent,” one of the tweets stated. Other tweets contained racist slurs against Jewish and black people.

Another tweet claimed there was a bomb at Twitter’s headquarters.

“Intel is there’s a bomb at Twitter HQ,” the tweet reads.

The tweets and retweets remained on Dorsey’s account for 30 minutes and were then deleted. But screenshots verify reports of the incident, which the tech giant is investigating.

Twitter shares fell less than 1% in after-hours trade following the hack, Reuters reports.

According to Digital Trends, a group of hackers known as the Chuckling Squad breached Dorsey’s account and sent out the offensive messages.