Tristan O’Tierney (pictured), one of the co-founders of Square, has left the company. He announced his departure in a tweet. Several other senior executives have left the company in recent months.

O’Tierney gave no reason for the departure. In terms of future plans, O’Tierney tweeted: “Not sure yet, except for a bit of travelling”.

He set up Square with the higher profile Jack Dorsey in 2009, creating the Square app for iOS that enables small businesses to accept card payments on iPhones.

O’Tierney is the latest to go in what has been a high executive turnover at Square in recent months. In May, it was reported that Alex Petrov, newly appointed vice president of partnerships, would not join the company. No reason was given.

Meanwhile, Rob van Behren, a highly rated engineer, left Square. Again, no reason was given.

Moreover, the company confirmed that Alyssa Cutright, vice president of international, left in March. Again, there was no explanation, although Square did hire Francoise Brougher as its new business lead, a role that encompasses international expansion.

Most high profile was the exit of Keith Rabois, Square’s COO, at the start of the year, after allegations of sexual harassment.