Complex sentence: The security camera footage, which has been broadcast internationally, showed the man in shorts and a yellow t-shirt taking off a dark-coloured backpack while sitting on a bench and then stood up and walked away while looking at his phone.
Split into simpler sentences: The security camera footage, which has been broadcast internationally, showed a man in shorts and a yellow t-shirt taking off a dark-coloured backpack while sitting on a bench. He then stood up and walked away while looking at his phone.