BlackBerry's management shakeup continued Monday with the exit of three senior executives, three weeks after boss Thorsten Heins stepped down and a deal to save the smartphone maker collapsed. Chief Operating Officer Kristian Tear and Chief Marketing Officer Frank Boulben, both hired by Heins, are leaving the company, according to a statement. Brian Bidulka also is being replaced as chief financial officer by former controller James Yersh, but will remain as an advisor for the remainder of the fiscal year. Earlier this month, BlackBerry abandoned hopes of finding a buyer who could turn around the company, after the spectacular failure of its new platform, launched in January. The Waterloo, Ontario-based company helped create a culture of mobile users glued to smartphones, but lost its luster as many have since moved to iPhones or devices using Google's Android software. BlackBerry still has some 70 million subscribers worldwide, but most of these are using older handsets, with the newer devices on the BlackBerry 10 platform failing to gain traction.In September, the company announced that it was laying off 4,500 staff -- or one third of its global workforce -- after losing $965 million in its last quarter as sales plummeted. On November 5, Heins announced he was stepping down as chief executive after only 22 months on the job, and would be replaced on an interim basis by longtime technology executive John Chen.