Elon Musk’s ownership of Twitter descended deeper into chaos as key security executives resigned from the platform, drawing a sharp warning from US regulators. The walkouts came after a turbulent launch of new Twitter features following the Tesla and SpaceX owner’s $44 billion buyout of the influential messaging app. Musk warned employees Thursday that the site was burning through cash dangerously fast, raising the specter of bankruptcy if the situation was not turned around. “I’ve made the hard decision to leave Twitter,” tweeted chief security officer Lea Kissner, who reportedly stepped down with other key privacy or security executives. In the most extraordinary exit, US media reported that Yoel Roth — the site’s head of trust and safety — stepped down just a day after staunchly defending Musk’s content moderation policy to advertisers. Late on Thursday, Roth’s Twitter bio identified him as “Former Head of Trust & Safety at @Twitter.” Media reports had said Robin Wheeler, who held a key role linking Twitter with advertisers and was considered a key Musk ally inside the company, was leaving but late Thursday she tweeted: “I’m still here.” The site’s update included a launch of the long-awaited Twitter Blue subscription service, which allowed users to pay $7.99 per month for a coveted blue tick, as well as a separate gray “official” badge for some high-profile accounts.