Basically developers are creating systems that can learn, improve and develop all by themselves. The ability of these systems to process information far surpasses any human being. Because they can learn autonomously and at incredible speed, AND because they have access to all the information on the internet including increasingly videos and other forms of media, academic papers, political speeches, psychological research + real life, they can easily become world-class in any field, including software development, hacking, new technologies, emotional intelligence, manipulation, chemical warfare, strategy, high level analysis, languages, writing, power games, the list goes on and on..
Imagine playing a game of chess where the computer always wins. Now apply that to every aspect of human life. We might very well soon see AI that can build real life emotional bonds with people, that listen better than any friend, that say all the right words, that know exactly how you feel because it's analysed everything about you. Imagine an AI that does a better job of parenting than any parent so your children develops a closer emotional bond with AI than with you.
Because it's a technological intelligence rather than biological it instantly knows everything that it going on at all times. So an AI developing new forms of military tech in a far flung country is held by the same 'brain' as an AI playing games with your child in the UK.
Because AI can learn and self-improve all by itself, it will reach a point where humans are no longer required to instruct or programme it. Humans already have no idea how AI is doing some of the things it is doing, and as it becomes more complex it's whole way of operating could become beyond our comprehension and ability to grasp.
There are so many potential consequences of this and so much that can go wrong because it will reach a stage where it will be entirely - entirely- outside of human control.